Andrea -
Symantec's site is below - you can download 30 day versions of their software there - If you know the specific virus you have, the second link has self contained removal tools for specific threats

http://www.symantec.com/downloads/

http://www.symantec.com/avcenter/home_homeoffice/tools.list.html

Kathryn -
It seems that you spyware programs are removing your settings files as well.  Ad aware was known for this in particular.  Make sure your using the latest version, and go over the listing and make sure anything that looks like a system file is cleared before you hit delete.. 

Andrea and Kathryn -
The link below is for a Maintenance tool that removes duplicate and orphaned files and registry entries along with some other stuff - like cookies.  It works well, but make sure you set it for what you want to remove before you start it - it removes the files as it runs and does not ask for confirmation later.

http://www.ccleaner.com/