According to this blog on TechNet, the DirectTV HR-20 HD DVR is a Windows Media Connect media client. If you connect it to your Ethernet network (that has a Windows Home Server on it), you can share music and photos from your server to your DVR and whatever display device is connected to it.
This is great news, since I am an unhappy Comcast cable TV customer, getting ready to switch to DirectTV HD. Comcast cable is way too expensive, and their Motorola DCT6412 III HD DVR is a piece of junk. It freezes up and requires a hard reset on a regular basis.