HEY YOU!!!! I need advice! I got this Compiuter virus on my laptop. The virus is cald windowsupdate.exe.exe.

It open a back door and download other kind of viruses into my PC. This virus is kinda wierd. No anti-virus program can detedt it! The only this that keeps me from frying is my windows 7 security.
Every start up windows 7 ask me if i trust a unknown publisher.

Any way, long story short. I can't get out of it's grasp!!!

Should I format my PC?!(With no back up because it in there....)