Windows – Booting from a cloned Windows 10 installation

I ran into this problem this afternoon. Your Mac's model must be in Boot Camp Assistant's list of supported models for the "Create a Windows 7 install disk" option to be available, so you must find out if your model is there and add it if it's not.

1. Go to Applications > Utilities and right-click on the Boot Camp Assistant app; select Show Package Contents, and open the Contents folder where you should see a file called info.plist.

   **By default you don't have permission to edit info.plist. My preferred way around this is to copy it to my desktop (opt-drag and drop), then rename the original to info_OLD.plist (not necessary to rename it, but if you screw up, at least you'll have the original backed up). Authentification will be required... just enter your password when asked.

2. Open the info.plist file on the desktop with Property List Editor (right-click, Open with > Property List Editor).

3. At the botton of the window is a list called USBBootSupportedModels. Click on the list and then click the Add Child button on the tool bar. Apparently your model must be the first or last item in the list – this didn't work for me when I accidentally added it to the middle, but it did when it was at the top. If you don't know your model number, click on the Apple menu and click About This Mac, where you should find the information. In Lion I believe you have to click "System Report" to get the proper information. My model was MacBook2,1 so the item I added to the top of the list was MB21.

4. Save the file when you're done. Now drag it back to the folder where the original file is (replacing the older file if you chose not to rename it).

When you open Boot Camp Assistant now it should give you the option to create an install disk.

**I haven't completed anything beyond actually getting the option available, so I can't comment on if the install disk will actually be created properly.

As far as I know, Boot Camp doesn't support external drives (with a possible exception of some Thunderbolt devices and CD/DVD drives). The Mac's boot loader only supports booting via EFI on USB and Firewire, whereas Boot Camp is BIOS/MBR emulation.

Windows 7 x64 apparently has a UEFI mode. I don't know if this is compatible with the Mac implementation of EFI. It certainly requires a 64-bit EFI - so only Macs that are compatible with Mountain Lion are even candidates for this. In any case, I haven't managed to pull this off myself, and the information I've found on the web is conflicting. Even if you can get the Windows install DVD to boot in EFI mode (how?), Windows will probably refuse to install to a USB drive.

So in summary, there's certainly no straightforward way to do this. It might be possible with some effort, but I haven't seen any reliable reports of success. (and I haven't had the time to try it myself with Win7 - I tried and failed back in the Windows XP days)