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I recently bought an install disk for Snow Leopard and before installation it tells me that It cannot install because my hard drive doesn't use the GUID partition scheme and I am not sure what to do when partitioning the hard drive-

I need some step by step instructions better than the ones given to me by Apple.

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It makes me wonder what was on that Mac before, since all OS X installations would need that kind of partitioning.

Note: You will need to erase your entire hard drive.

  • During the first installation screens, you should see a Utilities menu button on the top bar. Click it, and select Disk Utility.

  • Here, you can partition your drive. Click the Partition tab and select your partition scheme — normally, 1 partition is enough. Here, click on Options, and make sure that "GUID Partition Scheme" is selected.

  • Finally, click the Partition button to apply these changes.

For more info, check the official Apple Support page: "You cannot install Mac OS X on this volume..." alert in Installer

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I agree about the question of what was on it before -- if this is an Intel Mac, the boot disk should always have been GPT; if it's a PowerPC Mac, the 10.6 installer wouldn't have booted it; if it's not a Mac at all, you shouldn't be installing OS X on it. – Gordon Davisson Apr 13 '12 at 15:16
Actually, some hard drives are delivered partitioned and even NTFS-formatted. Mostly external drives or refurbished ones. – Bora Apr 13 '12 at 15:46

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