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Can't install MAC OS X Lion - Macintosh HD "This disk cannot be used to start up your computer."

I downloaded OS X Lion this morning and when I went to install it I got a "Screen - Select the disk where you want to install OS X." -- Had two disk my Macintosh HD and my Time Machine (both are 1TB). The top and most important is the Macintosh HD (999.86GB - 739.75GB available states "This disk cannot be used to start up your computer". What do I need to do to install OS X Lion?

20" intel-based iMac, Mac OS X (10.5.7)

Posted on Jul 20, 2011 8:48 AM

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174 replies

Jul 20, 2011 8:57 AM in response to Dancepal1948

Open Disk Utility & select the parent drive for your Macintosh HD from the list on the left. ("Macintosh HD" should be indented under the parent drive.) At the bottom of the window you should see a line listing its Partition Map Scheme. This should be "GUID Partition Table."


If not, you will have to reformat the drive with this scheme after backing it up. (Reformatting will erase all its data.)

Jul 20, 2011 9:22 AM in response to JohnTheMacGeek

Same here. Installed fine on my MacBook Pro, but not on my iMac. My disk also shows GUID Partition Table, but I too had the message that Lion cannot be installed on this drive.


I have a Bootcamp partition - configured within Bootcamp assistant.... Never repartitioned the drive, and I don't even get the option to create a recovery boot drive.. just a straight "Cannot be installed on this drive". 😟

Jul 20, 2011 10:06 AM in response to R C-R

I have since run Repair Disk Permissions, and Repair Disk (after booting from the Snow Leopard DVD to do a 'clean' repair) as per support's advice.


They then said to retry the installation.. only problem is - "App Store" tells me that Lion is "Installed".. it's clearly not. How do I run the installer again when App Store thinks it's already installed??

Jul 20, 2011 10:17 AM in response to Dancepal1948

Create a Backup Lion Bootable 10.7 Disk

Purchaseand download Lion from the Mac App Store on any Lion compatible Macrunning Snow Leopard.

  1. Right click on “Mac OS X Lion” installer and choose the option to “Show Package Contents.”
  2. Inside the Contents folder that appears you will find a SharedSupport folder and inside the SharedSupport folder you will find the “InstallESD.dmg.” This is the Lion boot disc image we have all been waiting for.
  3. Copy “InstallESD.dmg” to another folder like the Desktop.
  4. Launch Disk Utility and click the burn button.
  5. Select the copied “InstallESD.dmg” as the image to burn, insert a standard sized 4.7 GB DVD, and wait for your new Lion Boot Disc to come out toasty hot.

With this disc you can boot any Lion compatible Mac, and install10.7 just like you installed previous version of Mac OS X. You caneven use Disk Utility's Restore function to image your Lion boot discimage onto a external drive suitable for performing a clean installon a optical-drive-less MacBook Air, or Mac mini server.



If your using Mac's in a mission critical type environment or have third party hardware or software you must rely upon working correctly. It's advised to wait until all the bugs, driver updates, third party software updates and other issues are resolved before upgrading. This might take several months. Then if you do so, do one machine at a time and carefully test everything before full deployment.

It's also highly advised to backup all one's data either manually to a external powered drive in addition to TimeMachine and Hold option bootable Carbon Copy Clones etc.

Can't install MAC OS X Lion - Macintosh HD "This disk cannot be used to start up your computer."

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