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Problem clean installing Mountain Lion over Mountain Lion!

Discussion in 'OS X Mountain Lion (10.8)' started by datsmabowl, Jul 28, 2012.

  1. macrumors newbie

    Hi there,
    A few days ago I purchased and downloaded mountain lion. I intended to perform a clean install from a usb drive, but didn't have one to hand. Knowing I'd have to wait untill today to get hold of one, I decided to install ML normally in order to check it out before doing a clean install.

    I think this may have been a mistake.

    I have now put ML onto a usb drive successfully (it is recognised when I plug it in inside ML) but when I try and restart my macbook in order boot from it, it isn't recognised. I only have the option of booting from my local hdd or from ML's recovery partition.

    Perhaps this has something to do with ML already being installed, and therefore it see's no reason to install it again? This is pure conjecture, I'm certainly not that knowledgable.

    Any advice would be appreciated, I really would like to do a clean install.

  2. macrumors demi-god


    Then boot from the recovery partition...
  3. macrumors newbie

    I'm sorry, I don't understand how that will help me perform a clean install. I won't be able to format the hd from the recovery partition, as it is a part of the hd, surely?
  4. macrumors 68020


    The Recovery Partition is there so you can format and clean install your OS. It will only format the partition that your current OS is on, i.e. the Macintosh HD.
  5. datsmabowl, Jul 28, 2012
    Last edited: Jul 28, 2012

    macrumors newbie

    Thanks for your help, I sorted it.
  6. macrumors 65816

    why install Mountain Lion over Mountain Lion...? seems easier to just run software update.. unless you have a really really old build of mountain Lion Dev preview. Mountain Lion GM and Mountain Lion release are identical.

    ANyways, if your USB bootable drive is set up correctly, your hardware will always see it as bootable no matter what is already installed on any hdd/ssd. Just because you can read it when in an OS does NOT mean it was set up right to be bootable.
  7. macrumors newbie


    Had same problem.... Hold option key at startup, start from USB (must be created as Bootable from MLion install disk).... Use disk utility and format partition as 1.... Mac Journal..... Exit utility and start the Install process from thumb drive..... Make sure you backup pics, docs, movies separately.... Timemachine can re-introduce problems from the base lion os x, or from leopard....

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