I believe you can only get Halo: Combat Evovled on the PC.
No. There is an Anniversary edition that has been released only on Xbox, and the original Halo: CE can be downloaded off of Xbox Originals in the store.
Im Halo fan since it was started,now the game i waiting for is Halo 4. I love Halo:Reach and Halo 3 and all the trilogy. I have to say that CoD is not good.