|It's probably a virus,|
It is probably malicious and has corrupted your registry,
it might be a prank virus which just pops that up and annoys you.
Try to do a search on a program which scans your regestry for imperfections however thats risky too.
To be safe you might want to back up as much data as you can and reinstall windows.
You will want to back your files in "documents and settings" and program files".
If it is a virus it is probably in your "WINDOWS" file.