Another thing to think about is that more and more games are being developed for the XBOX 360 and then ported to the PC, and since the XBOX 360 doesn't support DX10, don't be shocked if there isn't a lot driving it. Also, I don't think anyone is making DX10 exclusive games (meaning you can't play them w/ DX9). Crysis was supposed to be one, but you'll see that wasn't the case.
On the x64 front, personally I stick w/ 32-bit for the time being only so I don't have any "compatibility" issues when it runs the programs in "compatibility mode" on x64 systems. I know quite a few people do it though, mainly because of the ability to access more memory.
So here's what I would suggest:
-Make sure you have a DX10 capable Video Card (and possibly sound card)
-Go with 32-bit XP for now.
-When/If you upgrade to Vista, go 64-bit
Of course, this is just one man's opinion....
Oh, and make sure it has a mirror on the visor for the little woman to put on her lipstick....

Açieeed! style by