|How much RAM memory do you have ???|
Most Virus and Spyware scans are likely to work better in Windows Safe-Mode.
Try System Restore to a date when all was good.
Start >All Programs >Accessories >System Tools
Using System Restore too many times can cause
more harm than good. After doing a restore
that does not fix a problem, then UNDO the
Restoration, and try another restore point, or
just do the UNDO.