I'm 18 and I enjoy new and old FPS games, Unreal Tournament is probably my all time favorite, but Call of Duty is fun too. I like Unreal Tournament because I have never owned a PC that couldn't run it. Every version of Windows from 95 to 8 runs it great (even NT 3.51 works well with it).
The only times I've ever experienced problems running UT have been on laptops with speedstep/cool n' quiet enabled, and this one oddball desktop with an Athlon 64 x2 (again, with CnQ enabled). Unfortunately, as a result of this one of my friends refuses to give UT a proper chance because his old laptop wouldn't cooperate with it. 😜 The strange thing is that he would probably enjoy it if he gave it a chance, because we used to play Quake 3 and tons of other old PC games all the time.
About running it on NT 3.51, I've seen screenshots of it, but I've never actually watched it "in action". How well does it run? Do any of the settings need to be set a certain way?