Hiring these guys has been some of the best money I've ever spent. There hasn't been a virus they couldn't flush or a problem they couldn't fix yet. Let's me concentrate on other things knowing that if I have a problem they are there. I have three computers they take care of for me, all for one annual fee. http://www.tuneuppros.com/
spywareblaster prevents things from getting on your PC in the first place & is free Very highly rated
you should never ever keep using a computer that was seriously infected, even if it has been cleaned. that is if it holds very confidential information. that's what IT professionals would say. just take your windows (or linux) cd and reinstall from scratch, then get a good antivirus on it and turn automatic updates and windows firewall on.
Hey Lorenzo Ad-Aware was the thing to use when I did my first real investigations into 'best practice' for security, a number of years ago. Can you tell me which if any program is now your #1 choice as a replacement for Ad-Aware? It doesn't have to be freeware.