You really need to run a system file check (sfc) against your OS (looks like XP?) to ensure all the files you have are valid Microsoft files.
I'd suggest:
- Running an antivirus/antimalware sweep.
- Reboot into safe mode.
- Run system file check.
- Run another antivirus/antimalware sweep.
If you can get or make a linux boot CD, boot into that, and then run an antivirus sweep from there, that'd be good too.