It's an ECS P.O.S. motherboard + an Athlon 64 3800 x2 , an eVGA 7900GT, and I've tried both the latest "release" and "beta" forceware drivers.
For reference I've also tried this on my main HTPC, which is an athlon 64 3700, some abit board (i forget), an nvidia 6XXXgt, and no attempt to update drivers. Assuming this HTPC is going to be underpowered anyway but perhaps it is worth pursuing.
Farthest I've gotten with HDDVD is that by demuxing the EVO with "EVOdemux", I can use cyberlink to play the .mpv (no sound) video stream. I can live without the menus but I really would like sound
Just a guess: the notes that come with the latest forceware drivers seem to suggest that "purevideo HD" (aka hdcp support) won't be supported under XP--only vista. I've got a copy of vista here but I've been trying reallll hard not to install it, because I honestly don't want to take a performance hit nor break something that already works for no good reason. I hear of spontaneous rebooting in dscaler in vista.