Lol....the pc is pretty much the original gaming platform
Ok, the mainframe is...or the ol' oscilator, really. Pong is the first console game, but that wasn't the first computer game.
Amiga, Atari, Sinclair etc etc...all 'personal computers'...
All MS is doing with Vista is trying to get a hell of a lot of people to buy their ME2.0...and they're enticing people with such musthaves as Halo2
But yeah, D3D10 is going to be a problem once some cool games go D3D10 only. I'm still warming the futile hope that more dev's will realise people don't need MS, don't like the MS tax and don't want DRM so they'll recode their games for Linux. But I think we'll have to look at the game dev's from India, Africa and parts of the far east for that push. Linux is growing there quite fast, and has been taken up by lots of businesses...which'll help spread it to the homes, making for an attractive install base for the devs.
So get used to gaming in Hindi or Korean for your linux gaming