|1st tap f8 on bootup and try to get into safemode with networking.|
Once in there download these free tools:
2- tdss killer
4- trojan remover
5- hitman pro.
Install them an run them in that order and clean out all they find.
If you cannot access safe mode, download them with another PC and burn them to a cd or use a thumbdrive and then load them on the problem PC.
If you don't know how to find these here is a simple How-To
That will help you gain knowledge as you repair your PC.
Some HELP in posting on Computing.net plus free progs and instructions Cheers