Friday, 8 January 2010

iMac (and general macs) "Error loading operating system"

I'm in the process of reimaging 15 iMacs which previously had windows and OS X installed. I updated one and reimaged it only to find when booting into windows it came up with the error "Error loading operating system". So I tried an image I'd used somewhere else. This came up with the error message "Missing operating system"

Thought this would be to do with the operating system so updated OS X to latest (10.5.8) and all the updates (EFI Firmware). Thought that would fix it but no luck.

Apparently the error message is something to do with bootpicker. Reading bootpicker help, a quick-fix isupdating bootpicker. Also typing in terminal:

sudo -s
printf "flag 3\nwrite\ny\n" | fdisk -e /dev/rdisk0

I've since updated bootpicker when the error message was "missing operating system". Trying it on another image as we speak.


Through trial and error I found that boot camp does not like Windows to be on the first partition on the disk. I think it's because it intends people to use Boot Camp Assistant which then partitions your hard drive for you, thus making the Windows partition at least the second partition.

I knew it would be something simple!!


  1. Can you explain how to move windows to another partition of my disk?

    1. I don't think you can 'move' windows to another partition. The preferred way is to re-install windows to another partition. Load up "Disk Utility", click on your main Hard Drive, click on "Partitions", delete the other partitions and press Apply, then add new ones. Use one of these new ones as Windows.

      You can always just run Windows as a Virtual Machine, and move this file from one place to another as you see fit. Virtual Box is free!