Upgrade the AV program with the latest files, and do a virus search.
Also, remove all spyware with either Ad-aware or Spybot.
If no luck and the problem happened within the last 5 days, then hold down the Ctrl key during startup, select 'Command prompt only' from the menu with the arrow keys, press Enter, at the C:\> prompt type scanreg /restore and press Enter, select a Registry that predates the problem, and press Enter.
(Note: All programs, updates, drivers, etc., that were installed after the date of the selected Registry will have to be reinstalled).