When I installed the latest patch for Fallout 3, it gave me an error, but now my game won't launch, any fixes?

I've already tried reinstalling and installing the patch again. Says something about a .dll file, even though I have a legal copy of the game, the patch won't work.When I installed the latest patch for Fallout 3, it gave me an error, but now my game won't launch, any fixes?
Delete the patch period?