My computers been messed up since the 28th of november, everytime i download something or get the automatic visa updates and i turn off my computer and i start it back up it returns to the same state it was in on the 28th, i've ran virus scans with McAfee, but it shows "0 Detected", i've tried spyware & adware scanners, i've deleted half the stuff i have saved on my computer, but nothing works, does anyone know what causes this?