Computer is a SPAM zombie...still

I cleaned up a friend's computer that was infected with several things (there's never just one, is there) by scanning with both AVG and Spybot, and going through the registry by hand. Both scanners found and cleared infections, and subsequent scans find nothing wrong. I had, in fact, taken the machine back to her with great confidence that I'd eradicated the vermin, only to have one of the symptoms reappear when connected at her place. Mind you, the symptom had not appeared when connected to my network.

The computer is sending out emails to various IP addresses, and the occasional name@domain address. I know it's doing this only because AVG email scanner keeps popping up from the task bar saying "Connecting to...". She doesn't even run an email client -- she uses Yahoo! webmail.

Her daughter's computer, on the same network, does not show signs of infection, and there were no external drives or memory cards attached to her computer when I returned it/set it up and the problem resurfaced.

I then tried installing ZoneAlarm, hoping to catch the felon trying to connect outward. By default, I allowed no programs access to the internet, other than DNS services. The problem occurred without so much as an "ahem" from Zone Alarm.

I'm at a loss to figure out what's still infecting this machine. Any ideas?

Go this route. and post in this thread.

http://discussions.virtualdr.com/sho...d.php?t=197917

Spybot is so old I gave up on it several years ago.