WIll this delete the pictures and videos I already have saved on the hard drive ?
Yes; reformatting a volume will erase its contents. Copy them to another drive first; you should be doing this anyway, as a drive may fail at any time.
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It is really important to use only a drive with the correct file system "MacOS Extended" with Aperture or the aperture library may become inconsistent and you may lose photos this way (iPhoto: Issues with FAT32-formatted drives). Only, If you need the drive to share data with Windows systems, the drive will no longer be readable from the PC, if you format it "MacOS Extended". In that case consider to create a second partition on the drive, one for your Mac, one for the PC.
yes -- formatting a drive erases everything on it
You should not reformat unless you have a backup copy of everything on the drive
LN
Will this delete my photos that I already have on the hard drive ?
