How to change background movie in CS5?

Question

When I try to delete a background movie it errors "cannot be deleted because it is in current use"  How do I detach it from the project to swap in another movie?

Answer 1

A third variation on these responses, all of which are correct.
You don't have to "delete" the current motion video in order to replace it.  Just replace it as Erik described using the pickwhip.
You can also delete it, in order to have no motion.  This is what Erik is describing as manually deleting the filename.  Use Bill's method to open the menu (or if open, click on the menu to select it),  Click on the motion tab, then click on the filename in the "Video" line, and hit the "delete" key.
I don't think you were actually asking how to delete the "old" motion asset from the project, but to do that, you must first remove it or replace it as motion in a menu.