Are you willing (and do you have Windows, driver and software installers and data backups to hand), to start from scratch? In that case, the starting point is not Eraser, but a Windows reinstall (not repair) which should start by formatting the hard drive. Eraser might be used later, when Windows has been reinstalled.
If there is any way you can get rid of the virus without going to all this trouble, I would do so. If you are really sure that your problem is a virus, disconnect the offending machine from any network, including the Internet, and if you can use another, clean machine to search the net for solutions.