After the public release of Windows Vista, Microsoft will soon start shipping PC games that are Live enabled. The XBOX Live service will then been known as just one part of a larger system (think XBOX, XBOX 360, PC, Windows Mobile devices like cellphones, and the Zune). PC games that are Live enabled will use a service called "Live for Windows" which will work a lot like XBOX Live. You'll have one global "gamertag" on all systems. You can even add to your gamerscore by unlocking achievements on PC games. HALO 2 for Vista will be the first such game. From an article at Next Generation:

"A key feature of Live for Windows titles will be a unified Gamertag across all platforms and the introduction of the popular Xbox Live “Achievements� into Games for Windows titles. Achievements earned in both Xbox Live and Live for Windows titles will all count toward a player’s single Gamerscore. Microsoft’s Vista-reliant version of Halo 2 will be the first game to support Achievements on the Windows platform."

This news comes from a meeting with Games for Windows executives in San Fransisco, yesterday. It is the first confirmation that I've seen that unlocking achievements on a PC game will contribute to your gamerscore.

Sidenote: I predict that Microsoft will soon increase the number of friends that we can have on our Live buddylists. For one, I think it's almost needed now. Gears of War is a huge online success. I've got a nice chunk of my buddlylist that is dedicated to GoW users. Another part of my buddylist is hardcore HALO 2 players. Then I've got friends that play a variety of games that I also play on occasion. What if ANOTHER hit title was released that was Live aware? I would surely find a handful of new gamers to add to my buddylist. Yet, my buddylist is maxed out as it is. When HALO 2 for Vista launches I could easily add 40 gamers to my list.