I run Adware and Spybot pretty regularly. And I've got McAfee Anti-Virus - although that's been since I've had problems. It tells me there are no infected files, but it does give a list of potential problems that I'm unable to delete.
I heave heard people praise Spysweeper as being able to find series problems, but that you have to be careful because it will flag valid registry entries as virii.
No files, huh? That makes it hard... I would recommend using AVG, but AVG and McAfee don't like each other and McAfee's better if you only use one.
Have you tried downloading and running AVG? I use both Norton and AVG alternately. AVG picks up stuff Norton doesn't, and you don't have to subscribe to it or buy it to run/update it.