install windows 8.1 to external disk
Here's how to install Windows 8 to an external disk on a Mac.
Note that, for reasons that are a bit of a mystery to me, you can't get the install to work with a USB 3 external HD. However, it's completely fine to install to a USB 2 HD and then image the drive over to a USB3 one.
- Install Virtualbox
- Install VirtualBox OracleVM Extension Pack. It's a separate download.
- Pull down the Windows 8.1 VM for VirtualBox from modern.ie
- Extract with The Unarchiver
- Import image to VirtualBox
- Connect USB HD to Mac
- In Disk Utility, partition the USB HD with 1 Partition of "Free Space".
- Unmount USB HD using Disk Utility
- Under "ports->USB" add the HD to the VM
- Enable USB2 in "ports->USB"
- Launch VM
- Open compmgmt.msc by typing it into Explorer
- Down in Storage Manager, format the unallocated space as an NTFS partition
- Install WinToUsb on VM
- By hook or by crook, get your Windows 8 ISO inside the virtual machine. In my case I did it over SMB from a fileserver, YMMV.
- Run through the WinToUsb setup, choosing the 200MB parition as the EFI partition, and the large NTFS partition as the system partition.
- Go brew some coffee, take a walk, etc.
- Turn off the Mac
- Hold down Option on boot, choose EFI boot
- Now you're running Windows.
If you want to copy over to a USB3 drive:
- Launch Disk Utility
- Partition your USB3 drive with 1 MS-DOS partition. Make sure the parition table is GUID, not MBR. MBR won't boot.
- Use WinClone to image the old drive. It's $30 at the time of this writing, but worth it if you're doing serious Windows work. The image that comes out the other side is tiny, <4GB in my case.
- Restore the image onto the new HD.