Since there are currently no PCs for sale offering graphics chips that support HDCP, this isn't yet possible.
Weird. I googled a bit and found this:
http://www.asus.com/products4.aspx?l1=2&l2=8&l3=0&model=1313&modelmenu=1
..and Asus is not the only company. Sapphire has some HDCP/HDMI cards as well it seems
http://www.boxgods.com/dept/htpc-sff/index.php?Action=Article&ID=215
The second reason, according to Bautista, is that BD playback software that can decrypt HDCP isn't "released as a saleable item yet".
Not that I have tried to play anything Blu-Ray -ish on my PC (well.. Sony, claims it is not possible anyway at this point), but I googled a bit further and found this. Cyberlink and NVidia believes it might work:
http://www.cyberlink.com/eng/press_room/view_842.html
http://phx.corporate-ir.net/phoenix.zhtml?c=116466&p=irol-newsArticle_Print&ID=870130&highlight=
That Cyberlink press release is well over a year old.