Yes, there's two versions: the DOS version and the 1998 Special Edition that uses the XvT engine. Simply select the DOS version and run that instead.
Just completed X-WING ALLIANCE using the ALLIANCE UPGRADE mod, which updates all the ships and visuals and applies an automatic widescreen update (you have to fiddle with the controls to make sure the cut-scenes stay at original res, otherwise they get stretched out hugely).
Still an excellent game, probably the best in the series. I know TIE FIGHTER gets a lot of love, but it pulls its punches too much (it never makes you do anything really dubious, missing the point of the "playing the bad guy" approach) and it gets ridiculously over-powered later on. Games are generally supposed to get tougher, but in the later missions playing as the TIE Advanced, Defender or Missile Boat (or even just the regular gunboat) you might as well have God Mode on. Nothing can touch you. XWA does get tougher as it goes along and the final assault on the Death Star II is just preposterously difficult. Still doable with some good strategy though. I also find XWA has the best AI, the biggest battles and also requires some deft command strategy as well as doing things yourself solo. The only real oddity is that Star Destroyers seem a lot weaker in XWA. It really shouldn't be possible to destroy them almost at will in a beat up old freighter.
I should pick up REPUBLIC COMMANDO. I only ever played the demo and by all accounts it's a great game.
I love xwa, but I do not like how the devs made everything a bad version of the x wing in terms of alliance vehicles...save for the x wing. I was hoping some of the more famous mods would help with that, but the one place I went to was such a cult of personality that it wasn't funny and there don't seem to be many other options. Maybe I can learn to program my own stuff somehow,but I'm not sure. Then again, every time I get into a y wing and it pilots like a slow x wing with an ion turret fixed forward, I get a burst of inspiration/drive...hmmm.