Virus recovery

I got hit by a virus. I’m not even sure what it was but somehow, it got by the virus software and the firewall. I believe that I have got most, if not all, of the problems fixed except for two. First, the virus has disabled my firewall. Whenever I try to reset it through administrator setting, it turns it off again on about 30 seconds. A not in my security centre sayd that some of the functions are veing controoled by “group policy”. I am running Windows XP home. How do I go about fixing this?

Secondly, when I boot up, it tell me that “kernals64” is missing from the system32 folder.

Can someone help me fix these problems? Thanks.