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

    Mar 2, 2011
    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 68020

    Oct 12, 2006

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

    Mar 2, 2011
    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 68030


    Oct 22, 2011
    Newcastle, England.
    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

    thread starter macrumors newbie

    Mar 2, 2011
  6. macrumors 65816

    Dec 28, 2009
    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

    Aug 15, 2012

    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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