Right-click the Start button and select "Disk Management". Create VHD: Select Action > Create VHD .
While Microsoft no longer hosts the pre-built virtual disks, they still maintain the standard installation media. Go to the official . windows 81 vhd download link
Mount your downloaded Windows 8.1 ISO by double-clicking it. Right-click the Start button and select "Disk Management"
If you have an old physical computer running Windows 8.1 and want a VHD of specific setup, download windows 81 vhd download link