OK, I obviously made my search a bit too fast it seems
Searching a bit better I found a solution that does not imply uninstalling MS drivers and software.
So here it is in case somebody else needs it:
MS Keyboard application do not manage keys in a standard way (surprise surprise...) so the solution is tu assign the keys a command and not a function
For play pause, use MC17.exe /command pause
For Next and previous, use MC17.exe /command next and MC17.exe /command previous
No need to specify a path: as long as MC is running it will get and process the command.