Sol, if you're trying to get 3D Acceleration working, you should look at the original release's binaries. I'm 95% certain they hex edited the GOG release so that the 3D Acceleration option does nothing. I just posted about this in another thread but I'll post it here since its really relevant to what you're doing.
I created a guide to get all of the games working on Windows 7 a few years back ( http://savingcontent.com/xwing
) and also updated it for Windows 8 recently so I have a good idea as to why there's no hardware support based on my experiments.
With Windows 7 you could get the games working in 3D accelerated mode using a compatibility patch. However, in Windows 8 this compatibility patch was not compatible if I recall correctly. Furthermore, with XvT and XWA in Windows 8, even if you did get 3D acceleration working it sucked because the framrate was super low.
So I'm guessing they just didn't have a reliable way to get these games working in 3D across Windows 7 & 8 so they hex edited the exe files to disable 3D mode even if you select it.
You may be able to compare the original exe to the gog one to see what needs to change to re-enable 3D acceleration. But there's also other changes (of which I'm not sure what each one does) that they've also made.
What would happen if you took the tie95.exe from a CD-installed and fully working version and put it in the gog-tie-folder?