[SOLVED] How do I delete picture files that are in use by another program?

unplanned bacon

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Jan 11, 2014
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I think Settings is using the picture files for the lock screen since they were previously used for the lock screen. I moved all my pictures to a new directory and then deleted them from their original location, but it left a few behind (and the containing folders) saying they're in use by another program. How do I delete them?