not legally
Halo: Combat Evolved runs just fine on Windows XP.
Yes, its instores to buy; A Windows Live game.
Only for Windows Vista, but you can use it on Windows XP, but that will stop Multiplayer from working.
yes you do, but there are hacks to make it work on XP
This is kind of a two-part answer, because I'm not sure about the question. 1 - Halo (the original) will work on XP, and should work on Vista. 2 - Halo 2 will only work on Vista.
Yes. However, you must make sure that the version of Halo 2 you are trying to play is the PC edition rather than the XBOX version. It should read "Halo 2 for Vista" or something similar. Now this does NOT mean it is only compatible with Vista. Halo 2 is compatible with Windows Vista and Windows 7, but not Windows XP.
Halo 2 was designed and released as a 'Game for Windows' and only works on Windows Vista. It is said, however, that there are ways to get it to work on XP. Emulation is another possibility to use the xbox version of Halo 2 on any computer.
Yes sadly you really do need Vista to be able to play Halo 2. There are a few cracks out there that sort of make it work on XP but so far there's been no real or legit way to fully play Halo 2 on XP. Sorry
Yes. You can.
Halo: Combat Evolved is avilable for windows XP and Vista, and Halo 2 is available for Vista. Both are available at retail stores that sell PC games, and online. Currently there is no PC option for Halo 3.
No. A few games from Microsoft, such as Halo 2, were modified to work on Windows XP because they did not actually use any Vista-specific features. In general, though, a game that says it requires Vista likely does, or at least will not work on XP without modification.