To play protected audio has been a bit more difficult until very recently, as no current video or sound card (no matter which hardware it has) supports the Protected Audio Path needed to get compressed multichannel audio (Dolby TrueHD or DTS-HD MA) from your Blu-ray to your speakers via HDMI. The fix, as Anandtech and others discovered, is to let your HTPC decompress the multichannel audio, and send it over HDMI as uncompressed 8-channel LPCM. The hangup then became that hardware did not incorporate enough bandwidth to accommodate uncompressed 8-channel audio over HDMI, or if it did, the drivers or something else didn't work.
Redemption (or at least a workable fix) finally arrived in summer, 2008. AMD's Radeon HD 4000-series graphics cards, NVIDIA's GeForce 8200/8300 chipset, and Intel's G45 chipset all support 8-channel LPCM and actually work. Technically, Intel's G965 and G35 chipsets also support 8-channel LPCM, but the drivers never made it a pleasant experience.