Windows 7 Folder pictures trouble

[mediocremusic]

I've been trying to add album covers to my music folders by using the customize tab in the folder properties. However, when I select the jpg I would like to use in the 'Choose File' menu, then click 'Open', nothing happens. A blank icon does not even appear. Where the folder preview should be, there is absolutely nothing. Any ideas on why this might be? Thanks.