dragoniv: Steam offers them for a similar price--I got them there. Runs very well under dosbox.
wild_quinine: This is where we see the difference between Steam and GOG.
Steam made no changes to Xcom to allow it to run, as far as I'm aware. And it shipped with a TINY disclaimer to the effect that it wouldn't work under Vista. I didn't see that till I'd purchased it, assuming, like an idiot, that if it was being released on Steam it would run on contemporary systems.
No such luck. Can I get a refund? Can I hell - this is Steam we're talking about.
GOG rules vs. Steam, you'll get no arguments from me there, but UFO, TFTD, and Apocalypse all run perfectly for me under both Vista and Vista 64. I've played several complete games of UFO and Apocalypse (very very happily I might add!!!)
They are the original versions but they use DosBox, they're not the problematic Windows port CE versions that I could never make run right. Sound (except for low pitched alien screams, for some reason), video, everything is perfect and they run at the proper speed. If you're having trouble getting them to run you might be able to find help on one of their forums?
That said, I would buy them again from GOG in a heartbeat if GOG offered these games.