does your internet explorer still work?
Run trend micro housecall http://housecall.trendmicro.com/
the scan will take a long tiem depending on your hard drive size(s)
when windows just about to go to the FIRST loading screen after you boot up press F8, you should get a menu with a list of options, click safe mode. log in as the administrator. from there do a system restore to a previous date.