Hey there,
I've also wanted to play this great classic game in multiplayer with my friends via LAN. After I found the fan-made custom installer that allows you to install the game under Win 7 64bit I was very hopeful. I thought it won't be a big deal to get the game running in LAN since it supports TCP/IP. Unfortunately, however, we couldn't get any LAN game running on TCP/IP.
The good news are that I finally found a working solution: the IPX Wrapper tool on
http://www.solemnwarning.net/ipxwrapper/. This utility emulates IPX support by tunneling network packets over UDP.
You just need to download the zip file and copy the 4 included dll files into both, the X-Wing vs TIE Fighter directory AND the Balance of Power directory in order to get both running. In addition, I've also executed the included directplay-w64.reg file which adds something to the registry. I'm not sure if this step is even necessary at all - maybe the dlls already work on their own.
After all, you will be able to play X-Wing vs. TIE-Fighter via IPX on Windows 7 64bit!
EDIT: Meh, seems to be working for 2 players only. In the hosting menu, the 3rd player alwas had a crash in our tests :/