Excellent wiki said:"Jump on "Play now"
This option will show you the options you have when pressing the big play button on the top of the Microsoft MCE remote (this is not the same button as the OK button)
o Pressing play will: play song (this is the same action as the OK button on an MCE remote)
Now Playing [always]
o Pressing play will: play the song and jump to the playing now screen
Now Playing [if multiple items]
o Pressing play will: play the song and jump to the playing now screen if there are more songs in the playlist