user32.dll file missing

I think I have to reformat my moms computer. I installed Avast and Sygate (both free versions). Avast the other day came up showing a virus on computer, she click on something but can not remember what ???, as she know very little about viruses etc. I think somehow she clicked on somthing else other than the avast tools to repair, delete, remove. According to her, program told just to shut down, did not see anything about deleteing, moving or repairing.

Now computer just re-boots can not get into safe mode. I did manage to get it to stop on system re-boots from safemode. Bluescreen message as Stop error C0000135 can not find user32.dll.

Any ideas other than reformat, I like to try to solve without resorting to that.

Computer runs XP (SP2), partition is NTFS, I have NAV 2004, but it can not read Drive C:\ , I think it can not read NTSF partitions but am not sure.

Try doing a http://housecall.trendmicro.com/ trend micro online virus scan,And wait until someone with better virus knowledge to help, you

I can not boot into computer, so can not goto any sites, only access I can get on computer is the DOS Prompt, even then I need to use NAV 2004 CD to get DOS prompt (:

Enter the recovery console and put that file back from the original windows cd. See if that solves it.