Do you have a firewall ?
One that provides outbound protection and XP’s (if that is what you have) doesn’t provide any. Without a firewall you will be fighting an uphill battle to remain clean.

Did you read these other forums I gave previously as they would appear to have the same problem ?
See http://forum.avast.com/index.php?topic=26554.0 and
http://forum.avast.com/index.php?topic=25941.0 this topic also provides links to on-line scans.

For software, just look at my signature that I would say is a good start point.

It looks like the rootkit is still at large, so you should also install and then run the other anti-rootkit tool.