Alright, so I go to run Descent 3 after installation, and I get this error "Error: SetCoopLevel EXCLUSIVE failed" I am running windows VISTA.
I have tried turning off the UAC suggested in another topic, my drivers are updated. Anyone have this error before or know what it could be?

I know the problem you're having must be frustrating but the games are working fine for most people on Vista and even on Win7.
You mentioned that you got 3 games from GOG and none of them work. That doesn't necessarily points towards a problem with the games, it might indicate that there's some problem at your end.
Can i ask besides Descent 3 what are the other 2 games and what kind of errors they give you ?
Also, you mentioned your drivers are up to date. How about your DirectX files ? You haven't mentioned those.
Rallack's suggestion about contacting support is probably your best chance of fixing the problem.

I just sent an email over to support this past weekend, just awaiting a response. I am able to run Descent on my XP machine, I would imagine, this has to do with Vista....
DirectX are up to date on the vista machine...I am really stumped with the error.

Yes, this one seems a bit tricky to figure out.
I really hope you'll get it fixed with the help from support.
If possible, post back to let us know what the problem was once you have it fixed.

I am having a similar error on my machine. I'm running Vista Ultimate X64, I've got more than I need for RAM and CPU speed and everytime I launch the game, the Dolby video plays then the game dings, crashes and I get this message...
Call stack:
------------------------------------------------------------------
main.exe 0056fa7c()
kernel32.dll 75c1eccb()
ntdll.dll 771ed24d()
ntdll.dll 771ed45f()
------------------------------------------------------------------
Plus some other stuff which it didnt copy. I have the error messge from the D3 folder, it is very long and I don't get a thing about it, but I have it if you are needing it.
I'm including a jpg of what it pops up saying when it crashes... Hope this helps in solving this mystery.

Can descent 3 be run in opengl rather then direct3d?

I am running it in OpenGL. I havent tried Direct3D. Perhpas that would work. I will try it now and see if that fixes it.
Nope. Direct3D still gives me the same error. I'm running a Geforce 9800 GTX + with 512mb DDR2. My drivers are up to datem I;ve got DX9.0c. Everything that this forum suggested doing.

jennaron0908 if you haven't done so already I would advise contacting gog support about your issue.

Jennaron, you say you're running 64 bit Vista? That kernel32.dll line seems to imply that it's looking for files in 32 bit Windows...
Randum, are you also running 64 bit? That could be the problem we're seeing!
Wait... Does anyone have this game working on 64 bit Vista?