I have suffered a similar infection recently and I managed to fix it by booting into safe mode (press F8 repeatedly during the boot up cycle before the windoze loading display occurrs) and then running system restore.
I must admit that I was doing it with a grin on my face as I had just replaced the computer (a laptop) hard disk and had the image of the entire disc on another machine, hence if all else failed it would be a matter of a quick reformat and then rebuilding the hard drive - a two hour job of waiting while my other computer did the business.
P.P.