First, AVG free can not protect from rootkits. It is seriously stripped down version. Get Avira or AVAST, they are better. Superantispyware is ok, but I doubt it will find more rootkits than malwarebytes.

You force want to try a Live CD antivirus. Also you can run MSConfig to check if any weird apps are starting up at boot. Try this for some thoughts on Live Antivirus CD – http://www.raymond.cc/blog/archives/2008/12/11/13-antivirus-rescue-cds-software-compared-in-search-for-the-best-rescue-disk/

I reflect it can’t be made a final conclusion, because there are so many types of virus, trojan or spyware. They’re of different malicious code. And yet it seemed to be hard to deal with. But I reflect it’s simple to get ride of these virus, spyware etc,. You just need a well known anti-virus.

I’ll give you a rank list of anti-virus most used by people not more than.

http://www.softcns.com/search/anti-virus_1.html

I personally recommend AVG Anti-Virus Free Journal 9.0 and Avira AntiVir Personal 9.0 for free use, and BitDefender anti-virus for discount. By the way, the address above is a most most discount place I found.

I hope it will help you a lot. ^_^