Your computer should have checkpoints, where you've downloaded particular programs, installed programs etc. They're should be at least one checkpoint on the restore calendar.
If you haven't got any checkpoint to restore too, the only option is too full restore your pc. Your computer must have come with a system restore disk, use that and start all over!
system restore is unreliable and doesn't always go back----restore points are created when you add/remove software or you create it yourself---restore points are also created automatically when you leave the computer idle with a screen saver running for maybe more than 30 minutes -----anyway press F8 at boot up and go into Safe Mode and see if there is a "restore my computer to last known good configuration" or something similar there and click .
system restore help. in windows xp
Linear Mode
