I currently have XP installed, and it seems to be working fine. I don't really want to install Vista yet...
Here's my question: When games that are compatible with Vista are released, will they also work on XP? Or is it just that DirectX 10 is only compatible with Vista? I'd like to clarify...

It depends on what you mean by "compatible" with Vista. :) There are already quite a few compatible games, and there will be even more in the future. :) The latest Lara Croft, Trackmania, and C&C3 are officially compatible with it, even though they don't use DirectX 10. By the way, almost all games work on Vista with the latest updates (I've checked: Starcraft, Morrowind, Oblivion, Battle for Middle-earth 2, Dark Messiah, GTA4, War of the Ring, and of course, our beloved Heroes 5. But there's a strange situation with Heroes 3... The Shadow of Death says it's for an unknown OS, while the Complete Collection works fine). :)
Soon, Crysis will be released... it's recommended for Vista and uses DirectX 10, but it can also work on XP... :smile43: