You might want to try an online scan to check if you do not have a virus.

Panda ActiveScan - http://www.pandasoftware.es/activescan/activescan-com.asp
Housecall - http://housecall.antivirus.com/housecall/start_corp.asp

or do an online spyware scan:

Pestscan by Pestpatrol - http://www.pestscan.com/
Xscan by Spywareinfo - http://www.spywareinfo.com/xscan.php

or download and install Ad-aware & Spybot-S&D then run a scan (while you are offline):
http://spybot.safer-networking.de/ and http://www.lavasoftusa.com/software/adaware/

If your system is clean from virus or spyware, your next option is to run a System File Checker because that error message means your Windows is corrupted as per my google searches. You need your XP installation CD to do this.