I recently reinstalled Fallout 3 on the same PC that I ran it on fine before but for some reason when I launch FO3 I get the "Please wait" slide and then it crashes. It did this before and after I patched it. I'm running windows vista if that matters,

Have you tried deleting the .ini file? You can find it in your My Documents\My games\Fallout3 folder...it is the configuration settings file named FALLOUT. Delete it and refire up the game to see if anything changes.