Dude, go to google.com (I forget the exact URL for this) and search for AVG AntiVirus. It's free and updates are very frequent. I'm not quite sure of a remedy for the problem you are having with ending the program running because you can't get into TaskManager. I had a similar problem yesterday. Somehow a website search program got onto my computer and would pop-up every time I started a program. I looked in msconfig for any start-up files, ran Ad-aware, ran AVG AntiVirus AND Norton AntiVirus, even did some registry searching and I still couldn't isolate the problem. Finally, I just said screw it and formatted...which isn't always a bad thing as long as you backup your files. But I would try AVG first and see if that helps you out. Good luck man, let me know how it turns out.
You can try going into Safe Mode ( F8 ) and deleting the files there, or, if you have a bootdisk, boot into DOS or whatever, then try it that way (I think it would work).