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I've just re-partitioned my hard-drive using Disk Utility. I shrank my Mac OS X partition and created a new one with the available space. However, after rebooting, the option to start under Windows is now gone. I only have the option to start Mac OS X.

Basically, my partitions were like this:

  • Mac
  • Windows
  • Data

After shrinking the Mac partition and creating a new one I get:

  • Mac
  • Fat32
  • Windows
  • Data

Does anybody know why the Windows partition was affected by this change? And how can I make it bootable again?

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If you go into disk utility and select the hard drive (top level) and then look at the info at the bottom of disk utility, does it state the drive GUID? –  hellothere Aug 22 '12 at 12:04
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First of all, can you still access your windows partition from OSX? Second, I suspect the problem is that the hybrid MBR can only hold 4 partition entries, which in this case end up being: EFI/protective, Mac root, Mac boot/recovery, Fat32. That is, the Windows partition got pushed out. To verify this theory, can you please open a Terminal window and give us the output from running these 2 commands: sudo gpt -r show disk0 and sudo fdisk /dev/disk0. They'll show the GUID partition table and the (hybrid) MBR required for bootcamp, respectively. –  pmdj Aug 22 '12 at 14:12
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1 Answer 1

If you resized Mac OS partitions creating new partition after installing Boot Camp and lost Windows in boot option, you can recover it back with following steps.

If your Boot Camp is Windows 7:

  • Insert installation disk for Windows 7, boot to it, and start regular Windows install process.
  • Keep going until you see a screen saying "Install now".
  • Choose the option below the Install button: Repair your computer.
  • On following screen select first option: Startup Repair.

When done, reboot holding Option ⌥ - the Boot Camp partition is back!


If your Boot Camp is Windows XP:

  • Boot to OS X.
  • Go to your Windows XP partition.
  • Locate in the root directory a file called boot.ini.
  • Open it with a Mac text editor.
  • Look for part that says partition(x)
  • (x) represents the number of your Boot Camp partition. Now, you should add 1 to the number. Example: partition(1) should become partition(2)
  • Save the file and close the editor.

When done, reboot holding Option ⌥ - the Boot Camp partition is back!

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