Recently I installed a blu ray player in m y HTPC:
-ASUS 8AN-E Motherboard PCIe 1.0
-XP 2005 MCE
To allow full HD audio I needed to update the video card & ended up choosing a Nvidea GT440 which is PCIe2.0
After installing the card,also new HDMI 1.4a cables to my AV & projector and updating the drivers it all worked (for a change!!) according to plan!
The sound control was automatically changed to Nvidea HD Audio & full HD audio streamed to the AV from the blu ray & to my ears ...happy camper
Pretty awesome really as my motherboard is now quite old & still running XP MCE, oh & the only other changes I needed to make to get the blu ray drive to function in the first place was to increase the ram (still DDR1) to 4gb & install a Athlon 4400 dual core processor, both now very cheap on EBAY!
and update all the drivers & Bios. I was dreading having to build a new one & changing to Win7, No doubt I will eventually but no need just yet
