Windows – How to make the Boot Camp partition bootable again

boot-campbootloadermacbook prowindows 7

I needed to resize my Boot Camp partition so I used Gparted to move and resize it. This seemed to work, except that now I can't boot into Windows.

I can boot into OS X just fine. OS X can recognize the Boot Camp partition and view its contents. When I try to reboot into Windows, however I get the message:

No bootable device — insert boot disk and press any key

The only solutions I've been able to find online suggest that the only way to fix this is to either clone the drive or remove the Windows partition and re-install it.

Is there any way to fix my Windows partition so that I don't have to reinstall Windows again?

Best Answer

It might be that your Windows partition is just fine, but it's your Protective Master Boot Record that's screwed up. Macs use the more modern GUID Partition Table (GPT) format to define where each of the partitions are, but for Boot Camp booting into Windows, you need a fake version of a traditional Master Boot Record (MBR) on the drive.

Apple's Boot Camp Assistant takes care of creating this "Protective Master Boot Record" or "PMBR" as they call it. Apple's tools are aware of the need for keeping the GPT and PMBR in sync, but perhaps GParted wasn't so careful.

There are third-party tools such as rEFIt that, among other things, can probably help you get your GPT and your PMBR back in agreement after some other tool has messed them up.

Or you might try using Mac OS X v10.7.x (Lion)'s Disk Utility to repair the drive. Make sure you select the whole disk, not a partition.

Another fix might be to use Disk Utility to slightly resize a partition, so that it has to rewrite the GPT and PMBR.