posted by Howard Fosdick on Mon 31st Dec 2012 20:26 UTC
IconLast month, I explained why I use generic desktops and laptops running open source software. They're reliable and inexpensive. But this presumes you can fix them. I believe that even those with no hardware training (like me), can identify and fix most hardware problems. To prove it, here's a quick guide. Feel free to add whatever I've missed.

Here's the outline --

Step 0: Identify the Problem
Laptop Unexpectedly Shuts Down
Computer Turns On But Won't Boot
Computer Won't Turn On
Computer Boots into Windows But Fails Somewhere Along the Way
Computer Loses Date and Time
Mouse Problems
Keyboard and Display Problems
Optical Disc Problems
Memory Errors
Hard Disk Problems


  1. Before you open up your computer, remember to unplug it. Unplug everything.
  2. Ground yourself! A smaller shock than you get from walking across the carpet kills circuitry. Buy a $5 US anti-static wrist strap.
  3. Enter error messages to Google to see how others fixed your problem. Why reinvent the wheel?
  4. Download your computer's User Guide and Field Service Manual if you lack hardcopies.
  5. A 2" long Swiss Army Knife includes a tapered screwdriver that fits nearly all PC screws for under $15 US.

Step 0: Identify the Problem

The first step in fixing a problem is to identify it. Don't jump to conclusions. Run free diagnostic software for problem identification:
Don't know if your problem is hardware or software? Run a different operating system. If the problem disappears, it's software. If you're using Windows, boot a live Linux CD to determine if your problem is Windows or a hardware issue.

Now that I've told you not to jump to conclusions, I'm forced to do exactly that in this article, due to space limitations. My bad!

Laptop Unexpectedly Shuts Down

There could be many causes for this one -- a short circuit, damaged electronics, and more. Most random shutdowns are caused by overheating. Laptops are prone to this because they cram so much circuitry into too small a package for easy cooling.

Every computer has internal sensors that immediately shut down the system to prevent electronics damage if the temperature gets too high. Since you can not relate the timing of the shutdowns to your actions, they appear random.

View your laptop's internal temperatures by running a free monitoring app. Download SpeedFan or other free monitors for Windows or use lm-sensors for Linux.

To fix overheating, ensure all fan(s) are spinning when they should. Unclog the air vents. Make sure you aren't blocking the vents by placing the laptop on your lap or pushing your desktop up against a flush surface. Don't pre-heat a laptop by leaving it in the direct sunlight or in a car window. Use the computer in an air-conditioned room.

Open the computer and remove dust, especially that coating circuitry. Since static electricity kills electronics, don't rub down circuitry with a dust rag. Blow it out with an inexpensive canister of compressed air.

If this doesn't fix your problem, you may need to replace the fan(s). Fans burn out as their ball bearings fail. If the computer has a CPU heat sink (a metal flange that draws heat away from the CPU), you may need to re-seat it. Anyone who's downloaded their computer's service manual can perform these procedures so long as they exercise care. Here are good generic instructions with pictures.

Computer Turns On But Won't Boot

You flip the Power switch on and your computer appears to start up. The power light goes On, the fans spin, maybe the disks kick -- but nothing further happens. You can't get into the computer's configuration panels to perform problem determination.

Some brands will give you "beep codes" or "blink codes" to tell you what's wrong. Look in the doc to decode them.

If not, this one's tough to diagnose. You need a methodology that helps you find the problem.

If you can't get to the BIOS panels, you have a hardware problem. Turn off the computer, open it up, and write down where every wire, insertable adapter card, and connector attaches to the motherboard and the devices. Record this so you can reattach everything later. Then disconnect every wire or plug from the motherboard, except for the power connectors from the power supply. Detach all devices. Remove all adapter cards and all memory.

Now you're down to a naked motherboard with its CPU, attached to the power supply. Insert one good memory stick into the first slot nearest the CPU, attach a working display (with a video card you know works, if necessary), and turn on the computer. If you can't access the configuration or BIOS panels now, the motherboard or CPU circuitry may be bad. Visually inspect the motherboard for leakage, especially near the capacitors and battery. You might succeed in cleaning up leakage, but most of those boards are goners.

If the system does display the BIOS panels, the motherboard and its embedded circuitry is good. One at a time, reattach each connector or cable or insertable adapter card. After reconnecting an item, turn on the computer. If you can still get into the BIOS configuration panels, you know that whatever you just attached is not causing the freeze-up or failure. As soon as you attach an item and the computer dies, you know that that component was the problem.

Here's an example. My friend's year-old computer completely baffled him. It would start up, display the "HP Welcome" panel, and freeze. He couldn't get into the configuration panels. I stripped the system down to the Motherboard+CPU+OneMemoryStick+Display+PowerSupply. Then I powered on and got into the BIOS panels, so I knew the motherboard and CPU were good. Then I attached each item, one at a time, and booted after each, and got into the BIOS panels. Until I attached the SATA disk drive! Then the symptom re-appeared. We replaced the defective disk and the system has worked fine since.

This methodology is time-consuming but it's a surefire way to identify a defective component. It identifies these problems:
  • Improperly seated or burned out adapter cards
  • Faulty devices
  • Loose or bad connector cables to devices
  • Wires that aren't properly connected to the motherboard
  • Improperly seated or defective memory sticks

Computer Won't Turn On

What if your computer won't turn on at all? Check the power supply and ensure the computer is getting electricity. Was it plugged into a live wall socket with a good power cord? Test the socket with a lamp. Don't assume that one socket in a power strip is working just because the other sockets in the strip work. If you just upgraded memory verify the seating of the ram sticks.

Check the wire that goes from the Power On button to the motherboard. If this doesn't connect you're not turning on the computer at all. Is the power supply (PS) working? Did its fan spin when powered on? Is the PS properly connected to the motherboard?  If you have a spare try the motherboard with another power supply to see if a burnt out PS is the problem. Find how to diagnose PS problems here. If you have a volt-ohm meter (VOM) verify the current.

If these procedures don't work, try the disassembly/reassembly procedure above. Sometimes you'll find a short caused by improper connection this way.

Computer Boots into Windows But Fails Somewhere Along the Way

If the computer boots and gets into the Windows start-up process, then freezes or fails, nearly always you have a Windows software issue rather than a hardware problem. To find out for sure, boot a Linux Live CD.  If everything works you have a Windows problem. This is a hardware article so I won't address how to fix Windows.

Computer Loses the Date or Time

If your computer loses the date or time across sessions, you probably have a dead battery. This is the little round watch-type battery that keeps configuration information across sessions, the CMOS battery.

Before you replace the battery, write it down any unique configuration information still in your BIOS panels. Then, pry it out and replace it. They cost only a few bucks. After you install the new battery, update the date and time and re-enter any unique configuration info into the BIOS. Here's how the battery might look on a desktop's motherboard:

 CMOS Battery
Courtesy: and

Mouse Problems

If you have a rollerball mouse and it tracks poorly, you need to clean it. Open up the bottom and ensure all lint is removed from the rollers that contact the mouse ball. Don't let any debris from this cleaning fall elsewhere inside the mouse.

If your mouse is optical, the only cleaning you need to do is to ensure that no lint is clogging the optical opening beneath the mouse. Sometimes optical mice don't track well on glossy or transparent surfaces, including some mouse pads.

If your plug-in mouse doesn't work at all, ensure the connection is secure. Verify the operating system is using a valid mouse driver. Test your questionable mouse on another computer or plug in a different mouse to your computer. Reboot and test. This shows whether you have a dead mouse rather than a software issue.

If your mouse is wireless, the most common problems are: (1) a dead battery (2) a wireless connection problem (3) device drivers that are not correctly installed, or (4) a dead mouse. Check the batteries first. Ensure the wireless adapter or USB linking device is securely plugged in. Verify the drivers. Use the wireless control program to diagnose and resync the mouse. Try resyncing the mouse by powering everything down, then rebooting.

Keyboard and Display Problems

If you prevent food, hair and other debris from falling inside your keyboard, you've avoided 90% of all problems. To clean a keyboard, detach it, turn it upside down and vigorously shake it. If this doesn't work, carefully pry off sticky keys and eliminate the gunk underneath.

Desktop keyboards are so cheap you might as well buy a new one for all but the simplest repairs. Laptops are another matter, with their embedded keyboards. See how to repair individual keys here. You can also buy a replacement keyboard for your specific model of laptop and install it. This is generically described here and model-specific information is available hereHiren's Boot CD includes keyboard testing programs.

What if you spill water or a drink onto your keyboard? Turn everything off immediately. Pull the power cord or push the Off button. Do not take the time to perform a graceful shutdown! The longer electricity goes through the electronics the greater the chance for permanent damage.

Do not touch or move the keyboard. Wait a full day to ensure everything has dried out. Then, turn on the system. If you're lucky it will work.

Cleaning the keyboard with rubbing alcohol or electronics cleaner may be in order if you spilled a drink that will become sticky after it dries. If you spilled water, don't bother.

The principle about wet keyboards applies generally to computer electronics. I've picked up computers left out in the rain or snow, let them dry out, and used them without any ill effects. Just dry them out completely before powering on!

Desktop displays are black boxes. The usual remedy is replacement. But verify you don't have a device driver or software issue before junking your display. With laptops you have to buy a replacement screen for your specific laptop model and install it. Here are generic video instructions for replacing a laptop display and here are model-specific instructions. Anyone can successfully replace laptop screens and keyboards -- if they download model-specific documentation and follow it.

Sometimes you'll get a stuck pixel on a LCD screen, a pixel that inaccurately remains an out-of-place color like green or red. Use a felt cloth to gently rub around the bad pixel in a circular motion. If you can get the pixel to light properly, hold the pressure there for a minute or two, and this often fixes it.

Optical Disc Problems

If your optical drive doesn't work new ones are cheap. But first check all connectors, ensure the OS recognizes the device, and that you have a working driver installed.

What if the problem is sporadic? Try cleaning the drive with these three cleaning techniques. Another possible cause is differing calibration between drives. It's possible to write a disc on one system and find another unable to read it. Determine if you have a calibration difference by testing multiple discs on several different drives.

You might find that your drive works well with certain brands of disc media but not with others. Media differences can cause sporadic problems even with healthy optical drives. Remember that there are many optical media standards and that you have to match them properly to the drives that use them. While current drives support muliple media standards, you can't always mix all media in all drives (DVD+R, DVD-R, DVD+-R, DVD-RAM, Blu-ray, CD-RW, CD-ROM, etc).

What if your problem is a particular disc? Clean the disc by gently rubbing it from the inside towards the outer edge. Remove any fingerprints. Sometimes wiping with a dab of distilled water will work. Other times, more aggressive techniques are necessary. This article has a progressive list of steps you can work through to restore a disc to a readable state. It includes my favorite -- cleaning the disc with toothpaste. Read the article before you try it.

What if a CD or DVD gets stuck in the drive? Look closely at the drive face and you'll see tiny hole. Stick a straight pin in there and push a lever that will mechanically push out the tray. Do this with the computer powered off since it is solely a mechanical procedure.

Memory Errors

Memory errors are easy to fix. Simply remove and replace the bad memory stick. The problem is identifying that you have a memory error, since many are transient (sporadic). If you suspect a memory problem, run an intensive memory checker utility like Linux's Memtest86 or Hiren's Boot CD. You can also set the BIOS to quick-test memory upon startup at the expense of a longer boot.

When you add memory into your computer, ensure it's seated correctly before booting. If the memory is not inserted properly most computers will beep and refuse to boot, telling you to re-seat. Hopefully no damage resulted. After adding memory, enter your BIOS configuration panels to ensure it's properly recognized before booting all the way into your operating system.

Hard Disk Problems

A million things can go wrong with disks. If it's a software problem, you can fix it. If it's a hardware problem, buy a new disk. Messing with faulty disk hardware is not worth your time -- with three exceptions:
  1. You need data only available from that disk (you didn't make a backup or it's not current)
  2. You need to save your copy of Windows (if you lose your hard disk, you've lost Windows and all your settings)
  3. You need to save critical installed applications (you can't reinstall because you no longer have the install disks)
A few generic rules of thumb:
  • Never open the drive enclosure (it is sealed to remain dust free and you can't fix anything in there anyway)
  • Download the disk drive manufacturer's free drive-specific diagnostic program. Some can mark off bad disk sectors and even fix disk errors.
  • Most BIOS's have drive diagnostic and test procedures. But often these are not as good as those you download from the drive manufacturer.
  • As long as the drive still spins you can recover all or nearly all of your data
  • You can get your data back by spending money instead of time by sending the drive to an expensive data recovery service. You can often recover any data they can, but only if you work slowly and conscientiously. This section tells you how.
Here are common disk symptoms and how to fix their underlying problems.

"Operating System Not Found"

When booting your computer, you might get an error message like one of these:
  • "Operating System Not Found"
  • "No Operating System on Disk"
  • "Missing Operating System"
  • "Invalid Partition Table"
These are all software errors. Your computer is telling you that the master boot record and/or the partition table on the disk are missing or corrupted. So it can not boot the operating system. Verify this by setting the computer to boot from CD/DVD prior to hard disk, then booting and running a Live Linux CD/DVD.

To fix a bad MBR or PT, run a program to rebuild this data. Boot a Live CD like Puppy Linux and select its option to rebuild the MBR and PT. Or use the very thorough free TestDisk utility. Here is a complete tutorial on it.

OS Detects the Drive But You Can't Access Your Data

Sometimes Windows knows a drive is present but won't let you use it, or it tells you the drive needs to be formatted. Or maybe it just shows a blank drive that doesn't contain any data. Or it won't show its properties or let you format it. Usually this means a software problem: filesystem corruption.

You can fix a filesystem to recover all or nearly all of your data.  Here is a quick list of fix/recovery tools (with more here):  

Filesystem: Free Repair Tools:

FAT32, VFAT TestDisk, Disk DiggerPCInspector File RecoveryUnstoppable Copier, Linux dosfsck utility
NTFS Lots of free and shareware tools here, Ubuntu's tools, DTIDATA's toolTestDisk
ext2, ext3, ext4
Use built-in Linux utilities like fsck, e2fsck, ddrescue, etc., TestDiskDiskInternals

It's possible to have a hardware problem that shows the same symptoms. Dirty contacts on the underside of the drive are one cause. This article has photos that lead you through how to clean the drive contacts simply by rubbing them with a pencil eraser.

Drive is Not Detected At All

First make sure that drives have fully connected power and data cables. You could get a variety of errors from this but "drive not detected" is common. Check the data cable connection to the motherboard as well as the side that connects to the back of the drive.

Another cause of "drive not detected" problems is a failed logic card on the drive. This is the circuit board attached to the underside of the drive. The board circuitry may fail over time due to the heat coming off the drive and the temperature differential from the powered-off state.

Take off the drive board and replace it with another. You can buy one on the web or take one from another drive. The key to success is that the logic board must be for the exact same drive. If not, it will not work. Obviously, you'll only go to this trouble if you really need the data on the drive and you have no backup!

Drive Makes Clicking Noises

This is the infamous Click Of Death. Drives make clicking noises when they have to move the disk arm multiple times to retrieve data. The drive is not functioning properly and this is its error correction procedure. Your drive may fail very soon! Copy any data you need off there immediately. You may have limited time so copy files in priority order.

If you can not get in to copy data off by normal means, here is a procedure that extracts data from even the most recalcitrant drives. It's more detailed than I can describe here but the key steps are:
  1. Hook up a second target drive to the controller (or you can use a USB thumb drive as the target)
  2. Use the Ubuntu Rescue Remix Live CD and its ddrescue command to copy the raw drive image from the failing drive
  3. Make the target partition active so you can access your recovered data
ddrescue tries every trick in the book to read the data off the target drive, bit-by-bit, regardless of what filesystems or partitions the drive contains. It will even try to read the data backwards. It's very effective, but it might take many hours or even days to get your data back. Like all the software in this article it is free.

Drive is Not Spinning

If the drive is not spinning, most people assume it is dead. Usually, but not always. Sometimes you can get a dead drive working again by hitting it or dropping it. Freezing the drive sometimes works. Be certain you have no alternatives before trying these methods because they may destroy your drive! Prepare carefully in advance. You might only have one chance to succeed and you don't want to blow it.

Add your tips to make this a better quick guide to fixing common hardware problems.

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Howard Fosdick (President, FCI) is an independent consultant who supports databases and operating systems. He fixes old computers for fun and charity. Read his other articles here.


Laptop-Repair.Info Covers all the basics Basic but comprehensive Good tips
Computer Repair with Diagnostics Flowcharts,
The Laptop Repair Workbook
Include flowcharts for diagnostic repair
Fixed4Free, Yahoo Answers
Post and review questions
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