Have you tried going in to safe mode to get access to the C drive? Then run adware/spybot/mcafee etc in safe mode. This should help quite a bit.
Also, a great forum...
http://forums.spybot.info/forumdisplay.php?f=22 , post logs of removal software, and they will help remove everything. I've used them a couple of times when I just couldn't get pesky things removed, and it worked great.