If your Bro wants to play UT3 with any AA he'll have to be using Vista/DX10. As for those waiting for DX10 to make it to XP... Try wishing in one hand and sh!ting in the other and see with one fills up first.

It might be better to set your sites on Windows 7, and hope you can hold out.
Also, you can find the OEM version of Ultimate (either x64 or x86) for $180. Though it's still not really worth it IMO. I only use it because M$ sent me a free copy... And, I keep an older system with XP on it for all those things that Vista refuses to do.