Maybe a sound card is in order and some speakers since my Bose 2.1 just went out a few weeks ago. I still can't get myself to upgrade to a CPU that just doesn't cut it as is. Even thogh the D950 does look tempting.
I heard rumors of non-backwards compatible DX10, but Vista will work in 2D or 3D modes so I don't see why it wouldn't work in XP. I think it's just for games using DX9.