Back to Boot Camp

After getting used to working with Boot Camp on my new Intel Mac, I decided to borrow the second partition for a few days to dual boot two copies of Mac OS X (which worked flawlessly, by the way). Once I was done, I assumed I could pop in my Windows disc and do a clean format-and-install over the second Mac OS X partition. Boy, was I wrong.

Windows Setup displayed only one “partition” as it saw things — the entire 160 GB drive. Not wanting to blow away my entire main Mac OS X installation, I was unsure of how to get back to using Boot Camp normally. Launching Apple’s Boot Camp Assistant utility presented me with unhelpful messages such as “The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by BCA for installing Windows” and “This startup disk is not supported.” What to do?

One fact I was sure of was that I did indeed have two real partitions on my hard drive. Disk Utility clearly showed two partitions under my single drive hardware device. Both partitions were formatted as Mac OS Extended Journalled (HFS+J) volumes, but Windows refused to see them as individual partitions, perhaps because it only comprehends the Microsoft-standard FAT32 and NTFS formats. Hoping to fix the matter, I used the diskutil command line tool to format the second partitions as “MS-DOS FAT32”, even though the Disk Utility point-and-click interface only offered HFS+ and HFS+J in its Format menu. diskutil noted that, because I was booted off the drive, the resulting partition would not be bootable.

diskutil‘s note about bootable volumes gave me an idea — boot from the Mac OS X Installation DVD and see what tools are available there. Upon booting the DVD that shipped with my machine and choosing English as my main lanugage, I found the Utilities menu at the top of the Installer. In there was a launchable copy of Disk Utility — the very same tool found in your /Applications/Utilities folder. It listed many more formats under the Erase tab for the second Boot Camp partition, and I happily formatted it as “MS-DOS”, knowing it would leave me with one HFS+J partition and one FAT32 partition. Erase and format was successful, so I rebooted and held down Option to force the OS selection screen to appear. [At this point I checked and found that, yes, Boot Camp Assistant will rediscover your partition and prompt you with the usual options. It must simply check for the existence of a FAT32 or NTFS volume to run properly.] I discovered moments later that it’s possible eject and insert disks while at this screen, so I popped in my Windows XP CD and let Setup begin once more. This time, Setup listed the following partitions:

E: Partition1 [Unknown] 200 MB (EFI)
F: Partition2 [Unknown] 133120 MB <The main Mac partition>
Unpartitioned space 128 MB
C: Partition3 (WINDOWS) [FAT32] 19052 MB
Unpartitioned space 126 MB

The C: FAT32 formatted partition was approximately the correct size, so I figured it had to be the correct choice. FAT32 can be limiting in file size, but Windows was able to easily re-format the partition to NTFS on the spot (Quick format is much faster than a full format). After babysitting the Windows installer for the next 30 to 40 minutes, everything was working again in Boot Camp land. Holding Option at startup is back to presenting the usual Macintosh HD and Windows operating systems, and booting into Windows is fast as it ever was.

Back to Boot Camp

8 thoughts on “Back to Boot Camp

  1. […] Collin Allen cuenta en su blog cómo hizo para recuperar una partición Windows con BootCamp. El autor se vio obligado a utilizar su partición Windows para instalar una segunda copia de OSX, cuando quiso recuperar la instalación descubrió que ni el programa de instalación de Windows ni BootCamp reconocían su antigua partición. […]


  2. I have a similar problem with my Intel iMac, except I installed Linux over Vista because Boot Camp was giving me problems about installing it. It worked great, until I tried to merge the drive back together and redo Vista. I’ll definitely try this – why I didn’t think to look on the install DVD is beyond me. I tried almost everything else imaginable. Thanks!


  3. Jay says:

    very similar problem excpet i tried to dual boot ubuntu and osx and and when i go to disk utility i have my
    macintosh hd
    boot camp
    Linux swap

    all in mac os extended (journaled) but i cant install windows over linux or disk0s4 as they dont appear when i hold option during startup only macintosh hd does, can u shed some light on this ??


  4. Ken says:

    I also installed linux over the windows partition and have Macintosh, disk0s4 and Linux Swap.

    How the hell do I get rid of them if bootcamp won’t start up?


  5. Eric says:

    That is all good but I cannot delete the other partition at all. I had made a partition a while back and now I want 1 single partition now and there is no way to do this – that I can tell.

    Tried disk utility and the only options there are to erase a partition but it does not delete it.

    Tried to run boot camp and it says – The startup disk must be formatted as a single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows.

    Any ideas how to totally delete the 20 GB partition and get back to just one w/o having to format the whole thing?


  6. Taylor says:

    @Eric That takes two steps:

    (1) diskutil list to get partition locations ( /dev/disk0s[#] )

    (2) diskutil mergePartitions EFI OSx /dev/disk0s[BOOTCAMP number] /dev/disk0s[Current OSX partition number]


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