There are problems associated with System Restore and viruses. A file infected with a virus gets backed up into a restore point, and, using a restore point just re-introduces the infected file back into your system.
If you are infected with a virus, the thing to do is turn System Restore off, and then back on again, to clear all the restore points. This guarantees that there are no infected files restored.
However, in your case, it does not look very promising that you will be able to use restore points.
Do you have any idea of which virus is taking over? Any alerts, etc., or what is it doing?
Also, do you have access to a clean computer to which you can download some programs and make an attempt to get rid of the infection?