abcjump - desparate...

Hi,
Mistakenly I installed on my computer a bunch of malwares: I had multiple crashes of svchost and explorer.exe, my computer became very slow etc. (All these symptoms accured as I connected to the web)
I fixed most of the problems by installing COMODO firewall so I could control the connections, I removed some strange software by regular software removal and also removed some strange entries from msconfig - startup.

I have only one very annoying thing left - the abcjump malware. I can't open search results from google, and other certain sites like this one, and in general my connection is very slow.
I tried running ComboFix as described here: http://forums.majorgeeks.com/showthread.php?t=168500&highlight=abcjump ,
but I got an error message stating the it is not a valid win32 application (I downloaded the file in another computer because I can't download on mine, and on that other computer I got the message as well).

I am running Vista. I have avg, comodo and windows defender running.

What should I do?

Thanks a lot in advance!