If you know when the problem happened you can try System Restore: Start>>All Programs>>Accessories>>System Tools>>System Restore
This will allow your computer to go "back in time" to a date when it was working.
Give it a go. Worst comes to worst, you can undo the restoration, or recovery your machine to its factory state but you will lose all personal files if not backed up if you take the option for recovery.
Good luck
Kash, April 2006