When it is really bad the only hope is to boot a standalone OS image off a CD or USB. You could then manually fix enough stuff to get the main os up far enough to let you load. Tends to not be simple. You must manually edit things like the registry without a lot of tools to help you. You will have to try to find instruction on how to manually remove the virus at least partially.
It tends to be easier to just boot a linux standalone image and copy all the files off that you really need....no programs though. Then format and reinstall the OS.
Now I will assume you tried the boot into safe mode with networking and that did not work either.