How much memory is on your video card? I would limit your main memory by at least that amount.
Actually, just to make it easier, limit the RAM to 1 GB, reboot and see if BD behaves any better. If it does you can play around with raising it until you start having performance problems again, and back off a bit until it is fixed.
If a 1 GB limit doesn't help, then it probably isn't the same issue as the with the >3GB RAM problem.
Apparently MS got rid of the hardware sound acceleration options in Vista. I don't know if that was moved out of dxdiag or taken out completely.
