Windows 7: Draging to burn list in windows media player

When creating burn lists with windows media player , previously I would simply drag a song from any other folder to the burn list. I've been playing around with media player recently for another problem , and now I can't drag a song into the burn list unless it is already in the DETAILS PANE of WMP ! It is much quicker for me to find a song in my own folders , rather than scrolling through the massive list in the DETAILS PANE.
What have I done that has stopped WMP allowing me to drag any song , from any folder into the BURN LIST. How can I get it back to how it was.

The standard answer would be to use a restore point if this is a fairly recent development and you did not knowingly make any changes in WMP configuration.

An alternative would be to use another burning application such as ImgBurn that lets you choose songs directly from a hard drive folder.