Run “Control Panel → Administrative Tools → Computer Management → Disk Management”

Click “Action → Create VHD” to create the virtual hard disk. Assign 64GB or more as fixed storage space.

Boot from your Windows 10 installation media

Select the language and enter the license key. If you are upgrading from Windows 7 or Windows 8/8.1, enter the original license key.

Select Custom Installation

When the list of available drives is displayed, press SHIFT-F10 to get to the command prompt.

Enter “notepad”, then press CTRL-o to open the file open dialog. Check the drive letters assigned to the different partitions.

Exit notepad and enter “diskpart” on the command prompt.

Enter “select vdisk file=<path-to-vhd>”

Enter “attach vdisk”

Exit diskpart and the command prompt, and click “Refresh”

Install Windows 10 to Drive “Unallocated Space” which is the VHD.