TSSHP (The System Shock Hack Project) is a project to reverse-engineer and recode (from scratch, but using the original datafiles) the 3D role-playing/shooter games from Looking Glass (System Shock and the Ultima Underworlds).
SS2 is very hard to run on XP, or so I've heard. I couldn't get it work either. And I tried with original, bought and legal version. There's some updates on their site, which should do the job, but apparently it doesn't. At least I don't know but one person who got it running. If anyone hears or finds out a way to get it working, please inform me. SS2 is superb game.