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MAC OS-X cannot be installed on this computer

Every computer has a particular configuration set inside its system. If there is a problem in installing MacOS with the same, there must be a problem with the lower configuration. The user must try to carry on installing Leopard 10.5 on the particular computer. The capacity of the internal hard drive should be known along with the right understanding of the techniques needed to install MAC OS. The user should not reformat the computer if he/she cannot find the backup. This would result in losing everything in the hard drive of the computer. So before reformatting once should back up everything on an external hard drive.


I recently upgraded HDD in my iMac 24" with 2.8GHz Extreme edition CPU. I tried to do a fresh install of Leopard 10.5 on it and got this message: OS-X cannot be installed on this computer.
Any idea? The system can see and format the new hard drive via the Disk Utility, but no installation is performed.


Here are some points to consider if you still don't succeed installing OSX 10.5 Leopard or 10.6 Snow Leopard, even following the excellent step-by-step advice of the experts:

Remember that "Macintosh HD" or "My Mac" is NOT your internal hard drive - it's only something on the drive. Now, if you try to install osx 10.6 (or 10.5 perhaps) and it says it can't install on "Macintosh HD", it probably means you simply have to reformat the DRIVE with the GUID option ticked. The GUID option will appear in Disk Utility ONLY when you choose to reformat the Toshiba or whatever drive. The option is NOT there if you try to reformat "Macintosh HD" because Macintosh Hard Drive is NOT a hard drive - lol ;)

The very last thing to do before reformatting your internal hard disk is to check that you really have backed up your disk on the external HD (borrow one if necessary). If you can't find the backup then don't reformat unless you don't mind losing everything on the internal hard drive. If you are using Time Machine don't be afraid if you only see a backup folder called Backups.backupdb The backup(s) are in there in another folder that might be called "Admin's Imac" - even if you're on a MacBook :o) If there's more than one dated backup, it's because you've backed up more than once - haahaa.

To summarise:
  • "Macintosh HD" is not a hard drive, but Toshiba whatsit IS

(you cannot reformat "Macintosh HD")
  • Your MacBook disk backup might be called Imac

I have just realized this after weeks of disappointment and wondering if my brain needed reformatting ;)

You might read that Intel macs are always formatted using the GUID option when they have at least 10.5 installed, but this was not the case on my 2GHz Intel Core 2 Duo MacBook.

Anyway, my 80G Toshiba internal disk drive is now GUID formatted and the system updated from 10.5 to 10.6 Snow Leopard. I understand that Apple says you should stay on 10.5 for the Core 2 Duo processor, but all my useful and up-to-date apps are working fine, and I see no speed issues (yet).
I accept that some of my old apps (old games) which worked on the previous formatting and OSX 10.5 may no longer work.
I'd previously installed Snow from the bought update disk on an empty partition on a 250G eGo firewire/usb Iomega external drive - it didn't flinch when I asked it to install and it simply did what I asked without saying "I don't like this disk" or "you didn't previously buy 10.5 for this partition so I don't want to be nice"

I've had macs since 1984 and stayed with them because you don't need to be a genius to use them (and they don't get viruses unless you install a dubious application from the internet, and they never used to freeze, and never needed mending etc - even though you couldn't just go out and buy one from any old supermarket), so I got really really peeved when it didn't do what I wanted.


Thanks to Presto for this tip on the forum.

A few words of thanks would be greatly appreciated.

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