[Morgeruat]

I only have a small bit to add, with Spybot S&D if you go into advanced mode there is a startup button on the tools tab, that will let you change the registry values of anything trying to start-up on your computer. Also the IE tweaks there can help prevent your browser's home page from being changed without your permission.

Being on DSL having a firewall is critical, if you've had DSL for a week with no firewall running, you can be sure that someone else has been using your computer for something. Zonealarm is a free firewall you can get from download.com