How do you get rid of the vundo trojan?

I have a computer that has vundo. I've tried vundo fix, spyware dr, spysweeper, trojan blaster, bazooka, spybot & nothing works. I've run it in safe and regular modes.When I try to install Spysweeper the vundo won't let me install it. When I run some of the programs in safe mode it says it removed it. But when I run it again in regualr mode it's back. I am pretty good when it comes to this kind of stuff but this has me stumped.