You really dont want Falcon 4.0. Allied Force was created for a reason and that reason was bringing it up to modern standards. It is more stable at the very least.
You'd lose a lot of details, for example, the gorgeous cockpit:
http://www.youtube.com/watch?v=v_wwike_5xk&feature=relatedBesides, if you dedicate time time to learn the complicated systems, you want them to be simulated as accurately as possible, IMHO. BMS is the reference.
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the only reason I need a copy of the origional falcon is so I can install BMS. It requires the origional game.
In fact you don't need a falcon 4 install, the BMS installer only needs to find a "falcon4.exe" executable (4.95 MB). You find that file, you can install.