Format an external disk for a Mac PC

Q I recently bought an external hard disk for my Mac that said it was ready to go on the box. It appears to be working because I can see the files that were included on it but I cannot save any files to it.

Every time I try to save a file to the disk a message appears saying ‘The item "filename" could not be moved because "New Volume" cannot be modified’.

Lester Peters

A The cause of this problem is that the external hard disk has been prepared for use with Windows computers using a system called NTFS. Macs can read files saved on disks prepared in this way but cannot change them or copy new files onto them.

The quick solution is to replace the NTFS system with a Mac one. This will delete all the files on the disk and render it invisible to Windows.

Click on the magnifying glass at the top right of the Mac desktop and type disk. Left-click on Disk Utility when it appears in the menu below.

Click on the entry for the external disk in the left-hand column. In our case it called ‘465.8GB Hitachi HDP7225050GLA360'. Make sure that you click on this and not the main hard disk in your Mac. As this process will delete everything on the disk make absolutely sure that you have selected the correct disk and that there are no important documents or programs left on it.

Click on the Erase icon in the main part of the Disk Utility screen. Select ‘Mac OS Extended (Case sensitive, Journaled)’ from the Volume Format menu. Give the disk a name (this does make it easier to use it later) and click on Erase. A message box will appear so click on Erase again to confirm the action.

The icon for the external disk will disappear from the Mac Desktop while it is being prepared and then reappear ready to use. Close the Disk Utility window to finish.

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