Ever since a seedy download on Monday the 29th, my computer has become...uterly screwed...

The file was downloaded and scanned with three trustworthy programs. AVG antivirus, Windows defender, and Tenebril Antispyware. Despite this barrage, the program's cover was not blown and I proceeded to run it. The program worked great and as soon as I was finished with it, I quickly deleted it. Still suspicious, I decided to deep scan my computer with the above mentioned programs. Please note, Zone Alarm was active and on high alert during this entire process. The search turned up nothing, Zone Alarm caught a program trying to update my IFP software (which I checked, rechecked and then warily granted access to) but other than that, my computer was clean.
What is another possibility is about a week ago when I was battling one of those viruses that just plants it's little processes all over the place, making the use of Hijack This and a friend geekier than myself an absolute must, the virus had not really dissapeared after all. Is there still some rogue process out there, opening the door into my computer for it's more harmful counterparts? Tune in tomorow during reformat for the exciting conclusion!

(Note: There's been some confusion about this, I don't actually plan to reformat. I have plenty of experience with virus fighting many friends who are even more experienced. They owe me a good turn as one of them owes his non single status to me :P If all else fails, I must, of course, reformat. But not without a fight! Remember the Alamo and the old Compaq in my basement, CHAAAARRRRGGGGEEEE!)