Maybe the intaller was made before Activesync 4.1, and therefore doesn't recognize it. On my pc it says I need activesync 3.1 or later, and I have 3.8!
I got the realplayer.cab file. It's posted
here Download this and put the file on your pocket pc. Run it from file explorer and it should install. If the program has problems, its not made for wm2005. By the way its version 1.1 :)