AntiVirus2008y

Alright i got this Malware from Mozilla Firefox and i basically just downloaded it a few days ago. i was screwing around with Firefox and a few days latrer i get a System Error Pop up saying.

Attention, Troy! Some Dangerous Trojan Horses detected in your System. Microsoft Windows XP Files Corrupted.
This May lead to destruction of important files in C:\WINDOWS. Download Protection Software now.

so i clicked no, and it sent me to a Website something like IEAntiVirus or something so now i ran ComboFix and it shows that i have AntiVirus2008y as my Malware or Virus...w/e u wanna call it. And i cant delete it. any ideas on how to delete it???