Here's what I found :

1. It could be one of the XP patches from MS; if you can get the updates to appear in the list, try removing one at a time (Then reboot) taking note of which ones you remove.

2. If you have an XP install disk, insert it and using the 'Run' command, type sfc /scannow to use the System File Checker which can determine if you have any corrupted system files. SFC will NOT run on XP without the install disk.