svchost.exe slowing me down

I've had problems with svchost.exe progressively eating up more and more of my CUP while torrenting for a while, and have decided to pretty much ignore it now, restarting my laptops in the morning to reset it so I can game.
Now, I've recently started playing the HL2 mod Dystopia alot, and it can just about run with all the settings turned off. However, every now and then, for about a minute at a time, my fps drops from ~40 to single figures. This obviously makes the game unplayable untill it recovers, and then it'll be fine for a while.

I just exited the game, and noticed that my svchost.exe is jumping betweeen 2-30% CPU usage, which I'm guessing it causing the fps drops.
Using process explorer, I see that its the Remote Procedure Call (RPC) service thats driving up the CPU.

http://img393.imageshack.us/img393/1657/processqp3.jpg

I ran a full AV scan with NOD32, and after googling the problem and seeing that it could be caused by the W32.Blaster.Worm, I downloaded the worm remover tool from the symantec website and ran that, just in case.
Came back to see that both scans found nothing, but when I tried to open firefox and MSN, the RPC service stopped, and Windows started a 60 second countdown to automatic shutdown.

So, I'm guessing that something is probably up, but don't know what.