So, "IIRC, I believe you need to run it in Windowed mode just until you get past that screen. " should be enough? Have anyone tried it (Win7 LAN)?
We will start friday evening, the worst thing would be if nothing works... :-]
/e: I found the following guide:
My steps to success are as follows:
On each computer:
1. Buy BG2 from gog.com, download, and install
2. Set compatibility mode on BGMain to Windows XP (Service Pack 3)
3. Run the game and switch to windows mode (alt-enter)
4. Sign up for game ranger: www.gameranger.com
On the host computer:
5. Host a BG2 game on game ranger
6. Wait for my friend to join the game on game ranger
7. Assign characters and start the game
8. Go back to full-screen mode (alt-enter)
9. Winning!
You may not need game ranger unless both computers are in the same network, but it made hosting a multiplayer game so easy that I definitely recommend it!
I hope it will work and I will post back if we succeeded! :-)