I have a virus, MS Removal Tool 2.20,I looked up how to remove it and i am required to remove associated files?

but i dont know how to remove associated files..or find them and also i need to get rid of related registry entries..but when i try to go to Run and then regedit a popup comes up and says i cant do that...so if anyone can help or give me directions how to get rid of this virus WITHOUT having to download any programs i would appriciate...