Or failing that, download clamwin for windows, install, update av files, reboot to safe mode no network support, and run it.

I just survived a hideous Sasser/trojan/host file attack a few weekends ago (have the screenshots of the port scanner saved somewhere just for fun), and I had to do that...a few times.

Also you may need to run msconfig and disable all the virus/trojan related startup files. Have fun with that.