Boot in safe mode, follow these directions:
START -> Programs -> Accesories -> System Tools -> system restore
click on "Restore My Computer To an earlier point", or something close to that. On the calendar that comes up, find the most recent recovery point and choose that. It could take about 10-15 minutes, depending on your computer, reboot and try it. That should work
AMD Duron 1.5
10/100/1000 Mps LAN
Windows 2000 Server
Windows XP Corp. Pro.
nVIDIA Geforce 6200a 512MB