Delete Media Libraries
To delete a Media Library, click on Media Library options button to the right of the Library name, then click "Settings."
You can also access Media Library options from the upper-left navigation:
Finally, click the "Delete Media Library" link at the bottom of the Media Library Info page.
You'll have a chance to verify your decision - click "Delete" if you're sure.
All media files in the deleted Media Library will also be deleted.