Backup and replace the original "BattlefrontII.exe" (which should be located in "C:\Program Files\Lucas Arts\Star Wars Battlefront 2\gamedata\") with the one you just downloaded. run "gamedata\BattlefrontII.exe" eg. "C:\Program Files\Lucas Arts\Star Wars Battlefront 2\gamedata\BattlefrontII.exe" SWF2 1.1 good to go
can only play multiplayer via lan or vpn (eg Tunngle)