very difficult I don't even know what I did.
it took me a while and I did all sorts of things but what I think sealed the deal was:
went to "turn windows features on and off" from add/remove programs, removed media player completely.
installed wmplayer 11 (this time had no errors) - and then removed it
went back to "turn windows features on and off", and installed wmplayer 12 again,
then I only had 1 file with a wrong version (wmplayer.exe - instead of 12.0.7600.16385, it was 12.0.7000.7000) so I searched the computer for the newer version,fownd it somwhere in wow64 or amd64 folder I think, replaced it (had to take ownership for that) and that's it I think...
somewhere in between I used a program to change file versions I dont remember when exactly or whats it's name.
hope this helps :)