Cant find Fallout 3 or New vegas error

[TristanTehGamer]

I have fallout 3 opened and the esp file in the data files but when I run vault tec multiplayer I keep getting an error saying "Can't find Fallout 3 or new vegas" anyone help?

[Henrik]

New vegas doesnt work try fallout 3

[Volumed]

You're using a old version in the first place.
We do not support old unstable versions.