Hmmm... I don't recall a problem with freespace 1 having problems running in XP. I think I got FS2 running as well, but after playing FS1 and FS1: Silent Threat, I was burnt out on the FS universe. That, and I really prefer the X-Wing style of combat for space sims. Have you played X-Wing Alliance? Great game, and can be found for as low as $5 these days. (and I'm saying it's a great game because, for a space sim, it is. I'm no star-wars fan-boy, I don't even own any SW movie.
If FS2 doesn't seem to run, check to see if you have the latest FS2 patch installed.