I'm a long time Halo CE online player - ATF Clan. My desktop still runs XP and I don't own an XBOX. I do have a Wii, though.
My wife and I both have Win 7 laptops and the only thing I use the desktop for is gaming and Photoshop printing of pictures from time to time. All my browsing occurs on the laptop.
Maybe as Microsoft's revenue continues to erode, they will find it profitable to release the later Halo versions for computer operating systems. They'd gain a lot of sales and a lot of popularity.