When a user launches Windows Media Player 12 (WMP 12) in Windows 8.1 he or she finds most recently used five playlists.
Resolution:
To hide most recently used five playlists in Windows Media Player try the followings steps:
1. Open Windows Media Player.
2. Right click on any item present in the sidebar.
3. Select Customize navigation pane, uncheck Playlists, and click OK.
Note: The same can be applied for WMP 12 present in Windows 7 and Windows 8.