FLASH: Unloading a movie clip?

[Michael Galvin]

I have a few buttons on my stage which run movie clips when pressed.  This bit works fine, but all the movie clips are at the same place on the stage, and when I press a button for the second time, it just appears underneath the one already there.  I've tried putting a transparent (same colour) background on the MC, but that just obstructs the second MC.

 

So how do I unload the first MC before running the second MC?

 

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