Try downloading, updating and running a full scan with the free superantispyware on your limited account.
http://www.superantispyware.com/index.html . This also has a handy feature that allows you to find out what's running on the PC. You could download the zip file on another PC, burn to disk and transfer to your PC if unable to download. If that picks up nothing then, if you can boot up from the xp CD , try an XP repair. Hopefully you have backups.
http://www.simplyguides.net/guides/r...ation_xp.shtml
Good luck.