apeman: Are you running the vanilla GOG installation or a source port?
My first thought is that you might be trying to run descentr.exe directly which I don't believe will work on a Windows 64-bit platform. The vanilla installation uses DOSBox which is actually what should be invoked with the appropriate conf file that's part of the installation.
If you're running a source port, like Rebirth, maybe it isn't finding some particular game resource, but I suspect it would complain as opposed to hanging as you describe.
I am running the direct download from GOG. downloaded it directly from the site and installed it no tweaks no other downloads. it just will not run.
CDN_Merlin: Descent 3 should not be run through DOS BOX as it's a windows app. You should be running MAIN.EXE
Also, make sure you run it as ADMIN. Try running it in XP Compartbility Mode.,
the GOG installer sets it to XP Compatibility mode by default and I have tried admin mode as well. same thing. It runs the process in the background, takes up 50 MB of ram... but never opens.