Spybot - Search & Destroy Configuration

Forget Spybot that's an outdated application.. and besides in the time I used it, it only found and deleted bad cookies.... it never found anything major... If you really want a good and effective anti-trojan, anti-spyware and in general anti-malware, I would recommend you use Malwarebytes Antimalware. And for even more stubborn and hard to detect bugware, A Squared Free is the most efficient application of the type I have used... it's a bit heavy (some 60MB) and the update definitions are another 70-80MB so put it off till you have no other option... and remove it if you have no further use for it.

So start with Malwarebytes Anti-Malware and if you need to recover administrative rights, use Subinacl.msi to reset to default security permissions.

Reset the Registry and the File Permissions in Windows XP
http://www.winhelponline.com/blog/reset-the-registry-and-the-file-permissions-in-windows-xp/