I have an HDMI but itunes tells me my computer doesnt support HDCP

I have a brand new system (PC) - High end graphics and a new dell HDMI 1080 display. I watch HD movies on it all the time. My machine even has a Blue ray. Yet Itunes tels me that it won't download a movie becasue my machine does not support HDCP...What's going on? I have Windows 8