Bootcamp Windows Partition Won't Boot After Accidentally Changing Boot-up Partition

Discussion in 'Windows, Linux & Others on the Mac' started by JordanSimps, Aug 13, 2013.

  1. JordanSimps macrumors newbie

    Oct 25, 2012
    I was messing around with the startup partition on my Windows 7 partition on my Mac and accidentally changed it to the Mac OS X partition. So when I boot the Windows 7 partition it says the error message "Missing Operating System". This error also shows up when I try to boot the Windows 7 DVD from the Mac drive selector screen. My question is how do change the boot partition on my Windows 7 partition if the partition won't even boot? I really don't want to install a new Windows 7 partition.

    Mac Specifications:
    Type: Mac Pro (Mid 2012)
    Processor: 3.33 GHz 6-Core Intel Xeon
    Memory: 32 GB 1333 MHz DDR3 ECC
    Graphics: ATI Radeon HD 5770 1024 MB
    Software: OS X 10.8.4 (12E55)
  2. wrldwzrd89 macrumors G5


    Jun 6, 2003
    Solon, OH
    You have the Windows 7 boot disc, right? Boot from that. Instead of installing, though, choose to repair a broken Windows installation.

    EDIT: How exactly did you change things? You might want to undo whatever you just did using the same tool.
  3. JordanSimps thread starter macrumors newbie

    Oct 25, 2012
    When I boot from the Windows 7 boot disc it says the same message "Missing Operating System". I boot the Windows 7 boot disc from the OS X partition manager.

    I changed the startup partition from Command Prompt while booted in Windows 7, so undoing what I did with the same tool is out of the question. I followed this tutorial to change the Windows 7 startup partition:

    Tutorial Link:

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