You'll not only have to format it, but you have to repartion it. Delete the current partition(s) and make new ones using the FAT(32) file system. Then fill again from the original or from your backup with all pics and video's you have.
I assume you know that an external HD isn't to be used for STORAGE. It's too error prone to contain the only copy of your data. But as a backup or as a means to listen to your Mac music on your PC and view your PC videos on your Mac it's nice.
Having a second or even third copy of everything on that external disk elsewhere also automatically means you won't loose any data when reformatting it.
Kees
hi,

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