I work on peoples computers part time to get some extra money on the side. Last week I encountered a disgusting virus (mmfav.dll as i recall) living in the system32 folder.
Heres where it gets tricky. Everytime the antivirus software or anti spyware software scanned for it, it shut down not only the program but the entire computer. So i tried to go in manually. I went into System32, targeted the file and the computer shut down. I went back in, tried to just right click on it, worked, then tried to delete it. I didn't expect it to work, and it didn't. (currently in use, as mr.gates told me).
So I tried just to target it with the anti-virus softwares manual virus vault. and the damn thing just wouldn't budge. Eventually I just fixed all the ways it was f**king up the computer, (i.e. accessing certian folders, and ip's) but it is still on their, probably doing bad stuff.
Someone suggested KILLBOX to me, thoughts?

Killbox is designed to delete files that are marked as currently being in use - ideal for removing viruses posing as system files and so forth. Care must be taken when using it not to inadvertantly delete a bona fide system file.

I'm not surprised that the anti virus isn't able to quarrantine the file - did you search for a dedicated virus removal tool? Many viruses and spyware applications that are around now are very difficult to remove, though I've always had success with dedicated removal tools that companies such as Norton provide.

Do you know what the virus itself is called? I tried to do a bit of research though the closest filename I got to the one you provided was fav.dll, which relates to a Trojan.NDrv. However, this trojan is a couple of years old and not reported widely as being particularly difficult to remove so I doubt that is the one you were referring to.

Let us know more and I'll see if I can find any alternative ways of removing it.

John