Windows Vista is only a little over three years old, but the version without any service packs installed will already move out of support April 13, 2010. This means you will no longer receive security updates from Redmond. The same holds true for Windows XP SP2; you will no longer get security updates for this release after July 13, 2010.
Microsoft advises you to move to Windows 7 (obviously), but also highlights that if you're not yet ready to do so, you should consider installing service pack 1 or 2 for Windows Vista, or service pack 3 for Windows XP. If you haven't done so already,
you deserve a spanking you should get with the program.
While both Windows Vista and XP still receive security updates when you install the latest service packs, this no longer holds true for Windows 2000. Support for all versions of that operating system will end July 13, meaning the time has now really come to move on to greener pastures.
"Customers running an unsupported version of Windows or service pack will not be eligible for any of our support options," Microsoft states in a press release, "Updates, including security updates released with bulletins from the Microsoft Security Response Center, will be reviewed and built for the supported versions and service packs only."
The server side of life will also face a number of support transitions. Like the desktop variant, support for all versions of Windows 2000 Server will end July 13, 2010. Also on July 13, Windows Server 2003 and Windows Server 2003 R2 will transition from the mainstream support phase to the extended support phase. During the extended support phase, security updates and paid support will remain available. Non-security updates, however, will only be made available to Extended Hotfix Support customers.Windows Server 2003 and Windows Server 2003 R2 will remain in extended support until July 14, 2015.