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I have a mid-2012 15" non-retina MacBook Pro with Mountain Lion. I have a 256 GB SSD in place of the original drive and an OptiBay in place of the optical drive where I put the original 500 GB Toshiba drive.

On the SSD I have OS X. I want to be able to boot into Windows 7 on the second drive but I also want to have half of the space sacrificed for my additional data.

First, I created a HFS+ single partition covering the whole second drive. Then I opened Boot Camp Assistant and ordered it to split the drive in half - it put a FAT32 drive as the second one, there is no other option.

Then, I created a bootable USB pendrive using Bootcamp. Because the Windows installer it didn't allow me to install Windows on the second drive, I opened my laptop and disconnected the SSD. Then I installed Windows without any hassle, updated it, installed applications, rebooted a few times - it all worked.

Afterwards, I reconnected the main drive. Now OS X boots fine but once I choose Windows from the list I get an "No bootable device" error. I suspected it's an MBR issue so I booted again from the Windows image on the pendrive and I tried to enter the "Fix my computer" menu item to go to the console and run fixmbr but it tells me I cannot run this option since my installed Windows version doesn't match one on the pendrive (?!).

As a last effort I listed all my partitions:

$ diskutil list
/dev/disk0
  #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *256.1 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:          Apple_CoreStorage                         255.2 GB   disk0s2
   3:                 Apple_Boot Boot OS X               650.0 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk1
   1:                        EFI                         209.7 MB   disk1s1
   2:                  Apple_HFS OptiBay                 249.0 GB   disk1s2
   3:       Microsoft Basic Data Windows7                250.8 GB   disk1s3
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS OSX                    *254.9 GB   disk2
/dev/disk3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *32.0 GB    disk3
   1:                 DOS_FAT_32 RALLY32GB               32.0 GB    disk3s1

(the 32GB-drive is the USB pendrive on which Bootcamp put its adjusted Windows installation image) and run:

$ sudo fdisk -u /dev/disk1
fdisk: could not open MBR file /usr/standalone/i386/boot0: No such file or directory

    -----------------------------------------------------
    ------ ATTENTION - UPDATING MASTER BOOT RECORD ------
    -----------------------------------------------------

Do you wish to write new MBR? [n] y

after a reboot I see a little changed disk order:

$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *256.1 GB   disk0
   1:                        EFI                         209.7 MB   disk0s1
   2:          Apple_CoreStorage                         255.2 GB   disk0s2
   3:                 Apple_Boot Boot OS X               650.0 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS OSX                    *254.9 GB   disk1
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk2
   1:                        EFI                         209.7 MB   disk2s1
   2:       Microsoft Basic Data Windows7                250.8 GB   disk2s2
/dev/disk3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *32.0 GB    disk3
   1:                 DOS_FAT_32 RALLY32GB               32.0 GB    disk3s1

but, unfortunately, the Windows option from the MacBook Pro boot menu is gone. :(

I honestly have no idea where to go with this from here... I'd be grateful for any help.

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migrated from stackoverflow.com Oct 16 '12 at 18:29

This question came from our site for professional and enthusiast programmers.

Install chameleon boot loader.

With this you can dual boot into windows or mac.

I have been using this since 2 years.

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When you install Windows you should format the FAT32 partition before installing. From the Bootcamp installation guide:

2 When you’re asked where to install Windows, select the partition named “BOOTCAMP.”
NOTICE:  Do not create or delete a partition, or select any other partition. Doing so may delete the entire contents of your Mac OS X partition.

3 Click “Drive options (advanced).”

4 Click Format, and then click OK.

5 Click Next. The installer formats the Windows partition using the NTFS file system.
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