I am trying to reformat disk using OS X Lion 10.7.5 but I keep getting the error "couldn't unmount disk" in disk utility

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I am trying to reformat disk using OS X Lion 10.7.5 but I keep getting the error "couldn't unmount disk" in disk utility

Posted on Aug 1, 2015 8:15 AM

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Answer 1

logic79

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Aug 2, 2015 12:57 PM in response to PaulusB

Are you trying to reformat the main HD that contains OS 10.7.5?

If you are then it won't work. You need to boot your computer from another OS startup disc.

Can you explain in more detail what you are wanting to do.

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Answer 2

PaulusB Author

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Aug 2, 2015 1:56 PM in response to logic79

Yes, I'm trying to reformat main HD. Finally succeeded by removing all the apps and files and especially the preference files and then erased through disk utility. I then reinstalled Lion and everything works. This machine is being given to a charity.

Mny thanks for your reply.

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