Taken from Wegotserved.com I would think this would work with windows 7 as well, with the Home Premium RD patch. So in short you would need to patch both the server and the desktop. Or spend hundreds more and by the PRO version.
You should note that the WHS server machine will Poll the clients and refresh information about them like IP address and, more annyoyingly the "OS Supported" Reg entry required for RDP access. So in other words, you can amend the WHS machine`s reg entry for your client to make it say "RDP supported=yes" and then an hour or so later WHS will poll the machine again, discover its a Home Premium machine or whatever, and put the value back the way it was before (i.e. RDP not supported on that client). Annoying.
The way round this is to schedule a batch file on the WHS machine which re-applies the reg change every 20 mins. Takes up zero resources and works like a charm.
TonyChan.Org Blogs - Remote Desktop on your Windows Vista Home Premium