If that's the reason, install VNC (some flavor of it) and enjoy. VNC works everywhere, though it's not as snappy as RDP for technical reasons. (RDP plugs into the GDI, but VNC is a sophisticated screen scraper.)
I was at my wits end, so the next step would be to try 3rd party software, but I really wanted RDP. The knowledge base here is, IMO, greater than Microsoft’s or any of the other blogs that go through all the elementary stuff over and over. Course you guys don’t know what all I’ve tried so I figure there will be some basic stuff thrown out there. I would think if I could get 3 machines going in about 1 min or less, I should be able to copy the same setup on the 4th machine. I’m figuring the “simple” fix will be something the help screens don’t cover, usually software from something else. I’ve watched bunches of Youtubes and they pretty much cover the basics. The Microsoft help boards do pretty much the same. If you Google it, you see many many others have the same problem, but alas, no answer as of yet.