Hi,
Method 1: I would suggest you to try the steps from the following link to delete skins.
Change how Windows Media Player looks using skins (To delete a skin)
http://windows.microsoft.com/en-ca/windows/change-media-player-skins#1TC=windows-7
Method 2: Try the following steps to delete Visualizations.
a) Press Windows Key + Q on the Keyboard.
b) Type Windows Media Player and click Enter.
c) Windows Media Player will currently open in the Player Library.
d) In the lower-right corner of the Player click on the Switch to Now Playing button.
e) Right-click an open space in the Player, point the mouse curser to Visualizations, and then click No Visualization.
Hope this helps. Let us know if you have any other issues with Windows in future.