My game is not installed inside the protected program files folder, I've got them in the default separate GOG Games folder.
I've tried running as administrator, and done a compatibility troubleshoot to no avail.
When I initially try to launch the game does ask if I want to install DirectPlay, I was under the impression that this was only necessary if I was planning on playing multiplayer.
From everything I've read, the lack of DirectPlay shouldn't be causing the inability to run BG 2.
I also have no trouble running Planescape: Torment, which is an Infinity Engine game.
A couple of others have had to install Direct Play when using Win 8.1.