The HaZardModding Coop Mod allows you to play the Single-Player Story and all the Secret levels Co-Operatively in Multi-Player. Supporting up to 8 players via LAN or Internet. Each Player can chose one of 3 Classes with specific abilities, to support the Team. Using the Tricorder primary scan mode when close to a Player, will activate the specific Class ability.
This small Tool allows you to switch between the patched(1.1)and un-patched(1.01) version of ST:EF2. So you can join both versions of the game each time, with just one single installation.