Think i had the same thing on my home PC. called it self AntiVirus2008. I did a ctrl alt delete went into task manager. Ended AntiVirus2008 in the processes tab and then deleted the AntiVirus2008 folder from my "C:\Programme files" folder.

This was quite a good programme i used to get rid of some other shite on my work Vista machine

http://www.malwarebytes.org/mbam.php