Hiya,
Thought I'd chime in here. I'm a big fan of the Descent games, I'd suggest giving one of the Direct3D patches a try, since they run under 98/XP. It can take some work getting the 3D version running on XP, but there is also a native software non-3d enhanced version included in the patch that will let you run Descent 1 in software mode under Windows, looking exactly like it did in the past under DOS.
So either way, you can get Descent with screaming 3D graphics, or you can run it non-3D mode at 300x200, 640x680, or even higher so it will look just as you remember it. (Trust me, 3D mode's the way to go here, I loved Descent, but in 3D mode it's so smooth!).
You can download the Direct 3D patches for Descent 1 and 2 at:
http://www.planetdescent.com/
Again, remember that though this is a 3D enhanced version, there is also a seperate Non-3D enhanced EXE file that will let you play under Windows. So if what you're really trying to do is run it so it looks/feels just like it used to under Dos, you can. (I still say that's madness though, since it looks the same just far sharper and smoother in 3D mode, just my opinion!).
Good luck.
Idaho