Steam – launch Fallout: New Vegas via Fallout 3’s launcher on Steam

Fallout: New Vegas uses Steamworks as its DRM solution, and therefore it requires Steam in order to play. Regardless of where you purchase it, you'll have to install Steam and install it via the Steam client in order to play it.

You can actually rename the FOSE or FOMM launchers to 'FalloutLauncher.exe', which is the executable Steam looks for when launching the game. Steam will then launch the appropriate program, but still think that it is Fallout.

For example, I did these steps with FOSE:

• Navigate to Fallout 3/New Vegas's folder under steamapps.
• Change the FalloutLauncher.exe file to be a different name, such as FalloutLauncher-orig.exe (in case you want to revert).
• Create a copy of the fose-loader.exe file, and rename it to FalloutLauncher.exe (Leave the original named as fose_loader.exe, as FOMM will look for this file when you launch FOSE through it.)
• Click Play in Steam. It should launch the game with FOSE.

I chose to do this with FOSE instead of FOMM, because FOSE launches the game directly. If I want to access FOMM, I still have it's link as a 'Non-Steam game'.