Can I use my Intel-based MacBook to boot into Windows 7 from an external HDD?

Can I install Windows on an external drive?

No. Installing Boot Camp on an external hard drive is not supported.

Boot Camp: System requirements for Microsoft ... - Support - Apple

No, you cant boot Win from an external HD or USB stick. no 😉

You seem to have a triple boot system that was done using the 10.6 installer disk and a copy of rEFIt.

I know because I had the same thing once.

I can tell you what will happen if you decide to upgrade 10.7 or 10.8

1: The EFI and GUID is going to change, rEFIt hasn't been updated in ages since 10.7 started rolling out back in about June 2011. There will be adverse effects with rEFIt so I hear.

2: The 10.8 upgrader is going to barf at your triple boot system, it will upgrade the 10.6 partition but warn you that the 10.8 RecoveryHD partition (10.7 and 10.8 both install) that it normally installs at the very bottom of the drive will not be installed and you can't enable Filevault.

Intel Mac's can have only 4 bootable partitions on the drive, the 10.7+ installer is normally dealing with EFI, MacintoshHD, BOOTCAMP, RecoveryHD. It barfs at anything else it doesn't understand and will not install RecoveryHD partition, which on a non-Internet Recovery capable hardware is required to reinstall the currently upgraded OS X operating system version. But you can always go back to the 10.6 disks and wipe and restore that way or via 10.6 USB boot key.

http://www.maciverse.com/install-os-x-snow-leopard-from-usb-flash-drive.html

So with 10.7+ you'll have to use something like Carbon Copy Cloner for the OS X partition.

So since rEFIt is going to be hosed, so will your ability to use the EFI based program to boot into the three operating systems at boot time.

I assume you found this out and why you want to dump Windows on a external drive. However Apple's EFI doesn't recognize Linux as a boot option.

There is a rEFIt fork that will allow Linux to boot on a Mac: http://www.rodsbooks.com/ubuntu-efi/index.html

Windows as you now know can't be booted off a external drive, however if your use of it is minor, you may want to consider using a virtual machine to run it in OS X or Linux instead using the free VirtualBox.

Windows in BootCamp or Virtual Machine?

You should Carbon Copy Cloner the OS X 10.6 partition to a external GUID OS X Extended J (JHFS+) drive.

You can use WinClone 3 in OS X to clone the Windows partition to a external drive, but it's a backup only, no booting capability. Restoring it will boot on the internal drive of course.

Linux you should already know how to clone it to a external drive using dd.

I advise you use the 10.6 install disks to set up your new partition scheme, but your going to have to uninstall rEFIt and return the machine and firmware back to basic Apple factory system as possible before doing anything.

EFI doesn't get erased, it resides in NVRAM and the EFI partition, controls the at boot key commands to boot off OS X install disks, so it's important to uninstall rEFIt completely before upgrading OS X.

If the Windows version your using is XP, to install that first using BootCamp in a fresh 10.6 install and reverse clone using WinClone before upgrading to 10.7 or above. It will be grandfathered in, but can't be reinstalled later.

This is very helpful info, ds. Thanks. Did you ever experience kernel panics or the like when you configured your system in this manner?

I'm probably going to wipe said drive and just use the entire partition for Mountain Lion.

What you mean to say is your going to wipe the drive and use the entire internal drive for Mountain Lion only, no Linux or Windows partitions.

I read it wrong and saw your signature that it's 10.6 and you plan to upgrade to 10.8.

And now your asking if you can run Windows off a external drive.

The answer is no but you can use a virtual machine if you don't want to setup BootCamp again.

If you want to preserve your Windows setup, you can use WinClone 3 in OS X to back it up to a external drive.

Then you can wipe and install using the 10.6 disks, then upgrade to 10.8 again so your virgin Apple.

Then setup using BootCamp and Winclone to reverse Windows back on, then use one of the commercial virtual machine solutions like VMFusion or Parallels Desktop that will image a BootCamped Windows to use a virtual machine.

Far as I know the free VirtualBox doesn't yet image a BootCamped Windows, but you can check it out if they did or not.

Once the virtual machine copy of Windows is made, you can use BootCamp Utility to delete the BootCamp partition and that copy of Windows, thus regaining your drive space for the Macintosh HD partition.

Make sure to use a virtual machine format in the commercialized versions that is compatible with the free VirtualBox solution, that way when your machine gets old and the commercial version doesn't provide updates, you can switch to the free VirtualBox that does.

nbar wrote:

Did you ever experience kernel panics or the like when you configured your system in this manner?

KP's are a OS X software problem.

The problems come running a outside EFI program (like rEFIt) in the firmware with Apple making changes to EFI.

The individual operating systems can have their own problems, but as long as EFI works, one can erase and restore the partition problems away.