If you are like me, and bought FO3 on steam, then you have a problem. Incompatibility. No longer! I have here some files that will save you some grief. I got my friend to patch his non-steam version of Fallout 3, and toss me his Fallout3.exe, I plugged it into my game, and Vault-Tec Multiplayer worked perfectly.
Here is the file:
https://dl.dropbox.com/u/11742779/Fallout3.zip
Enjoy!