I don't have much to add to Tony's response, except for this: I've learned a long time ago that actually taking the long route saves you some time in the end. By this I mean backing up the user data, formatting and re-installing and copying the stuff back will probably take you less time than trying to figure out this problem and trying to fix it with 'quick' fixes. Tony is more than likely right: the viruses probably broke something that is irreparable.