Riddled with trojans

Hey all,
I could find little information on this on the internet, so maybe someone could help:
A few days ago I opened internet explorer and had http://www.magicsearch.ws forced as my homepage and default search engine. Immediately curious as to how this was forced upon me, I looked at the running processes on my computer and noticed a strange one:

I deleted it, and a key it put in my registry, but that doesn’t seem to be a full solution. I look in the directory it was in and I see the following files that are the same exact size (23KB), three of which I KNOW are trojans:

So, my question is: Where can I find a fix or patch to a) kill the trojan and b) innoculate me from further attacks? I have that free virus scanning software AVG – but it didn’t even notice any of those files.

What can I do? (sistem.exe respawned itself, by the by.)

Sounds more like spyware than actual trojans (which would explain AVG not finding them) - I’d recommend a scan with one of the many spyware killers, such as AdAware or Spybot.

sisystem.exe is part of the CoolWebSearch spyware program. AdAware and Spybot have a problem removing it, but there is a good tool called CWShredder that cleans out all CWS components.