Minimum System

IBM/compatible running DOS 5.0+, 386/33+, 4MB+ RAM, hard disk

Recommended

486/66+, 8MB+ RAM, SoundBlaster or compatible sound card with General MIDI

Install Size

7MB (shareware) / 16MB (CD-ROM)

Works With

Windows 95/98, XP

Sound Notes
If you are going to run the DOS version of DESCENT under Windows 95 or 98, you shouldn't have any problems with sound as long as you have a SoundBlaster or General MIDI-capable ISA sound card (e.g. a SoundBlaster 16 ISA, Gravis Ultrasound, etc.); PCI sound cards are not likely to work.  With Windows XP, it will most likely not have sound, unless you have VDMSound installed.  For a better alternative for XP and up, see below.

Network Game Support
Requirements:Null modem cable (for serial play); 9600+ baud modem and ISP (for Internet play), or network card and an IPX-compatible network driver (for LAN play).

Notes:
• For IPX netgames in Win9x, simply installing Microsoft's IPX/SPX protocol does the job; if you want to run DESCENT in DOS mode instead of Win9x, once in real-mode type "net start nwlink" at the command prompt to enable IPX.  (I believe Windows for Workgroups 3.1x also supports this command.)
• For DOS 6.22 and earlier, IPX support is a bit more complicated; you need a minimum of three drivers to create the IPX "stack"—LSL.COM, IPXODI.COM, and a DOS driver for your network card.  I'm not sure exactly where to get them, but searching Google for "ipx dos" should help.
• DOSBox, of course, has its own IPX support built-in, so you might want to go that way instead of hassling with ancient network drivers and hardware to run the game.
• For UDP support, use D1X-Rebirth.

Where to Find It
Shareware:  Piece of cake; RGB Classic Games has versions 1.1-1.4 (just download 1.4).

Full Version (CD-ROM):  You're not likely to find it in an actual brick-and-mortar retailer unless you're lucky enough to know a place that sells old used software. 

Some places to look online:
• You can search for "descent pc cdrom" or similar on eBay (I bought a copy there) or other online merchants like Amazon.com; the same search should return hits for DESCENT II as well.  If you're lucky, you'll find one with the manual included.
• If you'd like to save money and the risk of buying it used, I recommend you consider the DESCENT I + II collection from Good Old Games, a digital distributor specializing in older game titles made compatible with modern hardware and Windows XP+, DRM-free, and sold at very low prices (the DI+II pack is $6—neat, huh?).  Be aware, though, that it's a 548MB download (mostly because of the D2 movies and Redbook audio).  GOG's DI+II pack is the same as the one that was sold as a 2-CD set back in 1996, except that it uses DOSBox to run.

Playing under DOSBox
DESCENT works well under DOSBox, as of version 0.73; both the shareware and CD-ROM/GOG versions are supported.

• I usually use a CPU setting of core=dynamic and cycles=max, with EMS enabled.  However, YMMV depending on the speed of your computer.
• Using DOSBox IPX:  In an IPX game using DOSBox, one computer on the network needs to be the server and all others to be clients.  On the server computer you would type "IPXNET STARTSERVER", then run DESCENT and host the game.  Clients would type "IPXNET CONNECT <hostname or IP of server>", then run DESCENT and join the game.  For more information, read the DOSBox documentation.

OS's Supported

Windows XP/Vista/7 (32- and 64-bit), Mac OS X, Mac OS 9, any POSIX-compatible OS (build from source)

Requirements

The original game's data files: DESCENT.HOG and DESCENT.PIG; these can be from the shareware, CD-ROM, or GOG versions; an OpenGL-capable graphics card.

Install Size (v0.57.1)

4.4MB (base) / 16MB (with game data)

Features
 

Macintosh PPC
Nearly identical to the DOS versions; requires a Macintosh PowerPC with Mac OS 7 or later.  (I do not know if it will run in OS X Classic Mode, but I doubt it would work well if it did.)  The CD-ROM version (distributed by MacPlay) requires the CD to run, as it uses Redbook audio, like DESCENT II.

Notes:
• I have yet to find a key layout on the Mac that suits my style of play; complicating matters is the fact that it's a PowerBook, and thus has a slightly different KB layout to begin with.
• With OS 8.5, USB support, and GameSprockets (or an actual gameport, if there is such a thing for Mac), you might be able to get a USB joystick to work, but I haven't tried yet.
•With third-party software such as MacIPX, you can play netgames between Macs, or (I suppose) other IPX-connected computers.

Availability:  The MacPlay CD-ROM is harder to find than the DOS CD-ROM or I+II collection, but not impossible; I found one on eBay at the same time as my DOS copy. So, as before, check eBay or Amazon.com.  I am still looking for a reliable source for the Macintosh shareware.

Sony Playstation (PSX)
Despite my classic gaming background, I don't have a Playstation 1 (or PSX, if you prefer), nor do I have plans to find one used, as I already have 4 old Nintendo systems to juggle (SNES, N64, GC, and GBA); nevertheless, I was slightly intrigued when I read that a version of DESCENT was made for the Playstation.  From what I've read, it's the same as the DOS version.

Availability:  I suggest checking eBay or Amazon.com; you might be able to find it.