You can try System Restore on your computer to a date when it worked well: Start - All Programs - Accessories - System Tools - System Restore. Then follow the Restore Wizard to complete the restore. If you can not do this restore in normal mode, you can do it in Safe Mode. To enter the Safe Mode, reboot your computer, when it starts, press F8. Select Safe Mode without Network. You must use administrator's account to log into Safe Mode.