Linked by Thom Holwerda on Tue 17th May 2011 12:23 UTC
"Whenever I connect to a WiFi network which requires in-browser authentication, such as university networks and hotel access points, Windows somehow magically knows. Windows also knows when your internet connection isn't working, and can differentiate between having local LAN access, no network access at all, or full internet access. But how?" Windows 7 actually phones home to a simple Microsoft Network Connectivity Status Indicator (NCSI) site for this functionality to work, and there, IP address and date of lookup are stored. Windows is flexible, however - you can turn this off, or even set up your own, personal NCSI server so that you will retain the functionality, but won't contact Microsoft. Pretty neat.