Trojan virus - HELP!!!

Turn off system restore by following instructions here
http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2001111912274039 for Xp
or here
http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2001012513122239 for ME

That will purge the restore folder and clear any malware that has been put in there. Then reboot & then re-enable sytem restore & create a new restore point.

then do this as well so we can check if you are clean everywhere else

go to http://www.thespykiller.co.uk/files/HijackThis.exe and download 'Hijack This!'.
make sure it is placed into it's own folder, not a temporary folder. Then doubleclick the Hijackthis.exe.
Click the "Scan" button, when the scan is finished the scan button will become "Save Log" click that and save the log.
Go to where you saved the log and click on "Edit > Select All" then click on "Edit > Copy" then Paste the log back here in a reply.
It will possibly show issues deserving our attention, but most of what it lists will be harmless or even required,
so do NOT fix anything yet.
Someone here will be happy to help you analyze the results.