So, you want to take the new Windows 10 operating system for a test drive but don’t want to risk your productivity to a pre-beta release?  Sure you could install it on a spare PC if you happen to have one of those sitting around.  If not, then dual boot is probably the option you want to go for.  Booting from a VHD is the safest route if you’re willing to sacrifice a bit of disk performance.  Fortunately I’m running a Surface Pro 3 with SSD and have sufficient time on my hands, so let’s get this party started.

What you’ll need.

  1. Windows 10 Technical Preview
  2. USB Key with at least 8G space
  3. Hard drive with at least 50G free space

Prepare the VHD

diskmgmtWhile Windows 10 Technical Preview is downloading, create a VHD to boot from using the Disk Management tool.

Click Action -> Create VHD

Choose a location for your VHD and specify the size of 50G (or more).  You should choose the VHD format and either a fixed or dynamic disk type although I recommend fixed size.  It will take a few moments to create the VHD and then you should see it in the Disk Managment window.VHD

Create a Bootable USB Key

Insert your USB key and then bring up a command prompt window using the “Run as Administrator” option.  In the command prompt window enter the following commands:

diskpart
list disk
select disk [number of USB key]
clean
create partition primary
select partion 1
active
format fs=fat32
assign

When these are complete copy the contents of the ISO to the bootable USB Key.

Install Windows 10 Technical Preview to the VHD

If like me you’re running on a Surface Pro 3, you’ll need to boot the usb key using one of the options below

Start from a bootable USB device when Surface is off

  1. Attach a bootable USB device to the USB port.
  2. Press and hold the volume-down button.
  3. Press and release the power button.
  4. When the Surface logo appears, release the volume-down button.
    Surface will start the software on your USB device.

Start from a bootable USB device when Surface on

  1. Attach a bootable USB device to the USB port.
  2. Swipe in from the right and then tap Settings.  (If you’re using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, and then click Settings.)
  3. Tap or click Change PC Settings.
  4. Tap or click Update and recovery, and then tap or click Recovery.
  5. Under Advanced Startup, tap or click Restart now.
  6. On the Choose an option screen, tap or click Use a device.
  7. On the Troubleshoot screen, tap or click Advanced options.
  8. On the Advanced options screen, tap or click the name of the USB device. Surface will restart and boot from the USB device.

When the Surface restarts the Windows 10 Technical Preview installation will begin.

  1. installtypeWhen you get to the setup step below, hit Shift+F10 to bring up a command prompt.  Now we need to mount the VHD we created earlier so that we can install Windows 10 from the USB key to the virtual hard drive.  In the command prompt window, type the following commands.
    diskpart
    select vdisk file=c:[your vhd file]
    attach vdisk
    After completing this you can exit Diskpart and close the command prompt window.
  2. At the next screen select “Custom:  Install Windows only (advanced)”  You should then see a screen that looks like the one below
  3. Select your VHD.  You may need to create anew partition using the advanced options.
  4. After you select the drive, the installation should complete and your system will reboot into Windows 10 Technical Preview.

installdiskAt this point, the installation is complete and your PC should be set for dual boot.  Windows 10 Technical Preview will be the default drive to boot to.  To switch back to Windows 8.1, simply select that option at boot time.

Hope this helps!