Check the items listed below in HijackThis, close all windows except HijackThis and click Fix checked:
O4 - HKLM\..\Run: [Antivirus] C:\WINDOWS\AV.EXE
O4 - HKCU\..\Run: [SpyKiller] C:\Program Files\SpyKiller\spykiller.exe /startup
Then reboot into
safe mode and delete:
C:\WINDOWS\AV.EXE
Regards,
Pieter