Make sure you have the messenger service disabled in the services. That's a back door to your system for spamware. Another thing is be careful where you go and what you download.
As for double crap, I use the immunize function of spybot S&D. Keeps more of the spam junk at bay. It's not perfect but it does work.
run the scan,then delete it, delete all temporary cookies/ files with something like Ccleaner then turn you system restore off and the back on.
Runninig it in safe mode is a good idea as Setishock mentioned.