Apparently a number of people are encountering an "endless reboot loop" - similar to what happened with Windows XP service pack 3 and Vista SP1 a while ago - when they upgrade Vista to Windows 7. The service pack problem was linked to the way some hardware vendors installed the Windows image on the machines. There has not been an official determination of the cause of the current problem. Some fixes have emerged, and they work for some people, but not for everybody. Read details here...
