I had the same problem on Me. I am not sure about Descent 1 but for Descent 2, you can open the descent2.sow file on the CD using something like Winrar and extract the files manually. The Vertigo installer seems to work fine though. However, both games run way too fast on today's machines (not just the framerate, the entire game goes 20 times as fast as it should; e.g. the ship bob looks like an earthquake and will make you dizzy in seconds
) and are completely unplayable. Since you are on XP it is unlikely that you will be able to get any hardware-based SB16 emulation to work anyway. Neither game works well with DOSBox, as the sound is all warped and for some reason your ship turns extremely slowly.
There are some Win95 versions out there that you will need to use to get things working and playable. For D1, you can use the fanmade D1_3dfx version, but you will obviously need a Voodoo2 or something like that installed. For D2, the 3dfx version is buggy and DOS-based, but there is an official Win95 version (software-rendered) that works pretty well. The game will probably still be far too fast to be playable, but if you run the game on the higher resolutions (to unlock these, use the command line -superhires) and turn off the cockpit, it runs perfectly. There is also an SDL OpenGL version of D2 out there, but that seems to have issues with the sound.
I still think D2 had some of the best fan-made mission packs of any game.
The cheats were top-notch as well and you could spend hours just playing around with those.
By the way, I finally got Lemmings 2 to work; the DOS version was having all kinds of issues, so I got the SNES version and an emulator and that one works perfectly.
