I would copy all important files to another hard disk before performing any repair. Perform a virus scan to those copied files.
Here's Microsoft KB for all the commands from Recovery Console:
http://support.microsoft.com/kb/314058
I remember a friend of mine was hit by "Windows XP Seruicty Risk..." virus and I have to do some extra steps to clean it up. I'm not sure if I used "FIXBOOT" or "FIXMBR". I think this is the right direction.