The first thing the virus/trojan did was probably to nuke your antivirus software.
Download Avast (
www.avast.com) using another computer onto a USB drive or somesuch (or your favourite antivirus program).
Restart XP in safe mode and use Task Manager to kill all instances of run.exe (I'm assuming through literate on the trojan that it runs through registry entries, not through rundll. Viruses which respawn through rundll are an utter bitch to remove) if any.
Try using your current Antivirus to scan and locate the virus, if that fails install Avast (or whatever), reboot again into safe mode and run a scan. Since it should come with very recentivirus definition files, Avast should locate the files (there are probably several), registry entries and so on.
Let me know if that fixes it (depends on how subtle the virus is and how far it has dug itself in).
To avoid such things in the future-
Create a separate normal user account for day to day use and an administrator account for installing/altering the system. It's inconvenient but you won't get this problem any more. Also make sure you have a good uptodate antivirus and firewall (zonealarm is pretty good for a freebie). Finally, go through Internet Explorer or Firefox and disable Java, most of Javascript and ActiveX controls. Firefox is better for this because you can change them on the fly without having to relog as Administrator.
If you're feeling brave you can also try the Windows Defender Beta 2 from Microsoft-
www.microsoft.com/defender. It's not perfect but it's another level of protection to keep you safe. Also make sure to scan regularly with Adaware (
www.lavasoft.com) and Spybot, but if you run as a standard user most of the major nasties won't be a problem any more.
Due to Windows file permissions system being broken, however, it is inconvenient to do so. That is set to improve however with Vista (hopefully...).
