Hey there Powers. I'm using the same exact remote as a temp for my prototype CarPC. Mine works great for what you're asking it to do... but here's how I've set it up. I do not have the remote enabled... the RemoteWonder acts more like a keyboard, so what you have to do it clear your keyboard command list and then reprogram your keys to use for your remote. For your "Up" keyboard key, press the up arrow button on the remote... same for down... On your select, press the "Ok" key in the middle of arrow keys. I then programed the vis. for the #1 button, the music playlist for #2, back for #7... and then the other numbers, well I programed them for something but thoses are really the only ones I use for it. The play and stop buttons of the remote don't seam to work, as they're the same funtions as any media buttons on other keyboards, remotes, what-not, and MediaEngine does not want to work with them. It does the same for my MediaCenter 2005 remote.
So, use your ATI RemoteWonder for now... but as I'm going to have to do, you're going to have to buy a (cheap looking) X10 remote, as MediaEngine doesn't work well on the play / stop / ff / rw buttons. Good luck.