Trojan in registry that returns after reboot

I ran all the recomended programs and followed all the steps, and it removed most of the problem, but there's one trojan file in my registry that refuses to budge. It's listed as being called 'Trojan.Generic' in HKLM\Software\Microsoft\Windows\CurrentVersion\Run\159f2487.exe I've tried to remove it with various programs (Trojan Hunter, Windows defender, Spybot search and destroy, trojan remover, a-squared, and quite a few others, most of which I found here. I know you said not use multiple programs, but some of them seem to be unable to detect this trojan, as it doesn't show up in the scan, and sense none of them removed it effectively I thought I'd try a few different ones. I removed the ones that didn't work after I was done with them.) to no avail. It's always back after I reboot. It doesn't seem to affect my PC (That I notice) beyone the fact that my desktop is locked to where I can't change the wallpaper and the windows firewall won't let me open the control panel. It always has an 'unknown error' everytime I try.

My computer is a Compaq laptop with windows XP, 512MB system memory, 80GB hard drive, 1.8GHz, 512KB L2 cache with up to 1800MHz system bus.

I'm running out of ideas for how to fix this problem, and being rather a novice with technical things I really don't know too much about what I'm doing and I'm hoping someone can give some advice for how to fix this problem.

 

Well, I think I fixed the trojan atleast. Reran highjackthis on a whim and when I restarted, it was gone. Hopefully it'll stay that way. But the firewall and the desktop still aren't working... I don't suppose anyone has any ideas on what that could be?