Hey paddyc,
Some backdoor trojans are very good at hiding themselves from anti-virus detections. I'm not really sure whether Avast's detection is better or AVG8's better, but I do think that AVG has fallen significantly in quality since the company combined AVG anti-spyware and anti-virus into a commercial pack.
Spybot has been a very good program, but unfortunately, it is becoming outdated with the speed of the emergence of all kinds of malware. It's definitions are not as updated as it was, not to blame the author of Spybot, but how fast malware are being written. Ad-aware, in my opinion, is only good with its paid version. Since Ad-Aware SE personal expired, Ad-aware has been full of problems, at least it is for me. The problem is, Ad-aware in its free version does NOT provide protection against spyware and adware (it's merely a scanner), but Spybot does.
You made a very good choice putting Zonealarm, Spywareblaster, MBAM (Malwarebytes' Anti-Malware) and SUPERAntispyware on your computer. These are probably the best combination of softwares that you can have. But both MBAM and SUPERAntispyware only provide resident protection against spyware in their paid versions, so if you want the maximum protection, I would suggest that you spend on MBAM and enable its full version protection. I think MBAM is worth the expenses, its wonderful both in its free and paid version. I would also say that using Firefox 3.0.4 and installing McAfee Siteadvisor would enhance your protection. Firefox is much faster and safer, and McAfee Siteadvisor warns you before you visit any malicious sites. McAfee Siteadvisor is installed as an add-on in Firefox.
Just to share with you what I'm running on my computer: Avast, Comodo pro free firewall, MBAM, Spywareblaster, McAfee Siteadvisor and Spybot. My computer has been without serious infections for months since I installed them. (Only an occasional malware sneak past my protection layer, but I detect them almost immediately because I run analysis tools like RSIT and ComboFix often.
Though, I'm not advising you to run RSIT and ComboFix because they are complex tools that can mess up your computer if you don't know what you are doing.)
taskmon.exe is a valid system application, either it could be a False Positive from Avast, or a hidden malware is using it to do things that you don't know. I would advise you not to do anything to that file at the moment and post a HijackThis log in one of the following free tech help sites and let a malware removal expert help you:
http://www.bleepingcomputer.com/forums/http://www.geekstogo.com/forum/http://www.techsupportforum.com/Many of them have a specific forum for
HijackThis log analysis, look for these forums, register an account and follow the instructions given to post your log. Just post ONE log in ONE of the above forums, don't post at multiple forums or post multiple topics regarding a similar issue. The experts there are all busy people, wait patiently for a reply. These forums usually have a place to raise your thread to the experts' attention if it hasn't been looked at for a certain period of time (usually 3 to 5 days). Look for these places if your problem has not been looked at for an extended time period.
Yah changing your password on a clean computer is probably the most important thing you need to do, don't use the infected computer for any online commercial at the moment. Get it cleaned at one of the forums I've suggested, and then look at the advises given by the expert. It is almost guaranteed that a computer can never be 100% clean even with the most updated and powerful protection package, but there are some measures that you can adopt to minimise the possibilities. The reason for having protection softwares is not just to remove any malware that sneaks in, but also to alert the user of a possible infection. Be on your guard, and take actions promptly when something goes wrong, that's the best thing you can do.
