Right-click This PC > Manage > Disk Management [1].
format is recommended over the older VHD. It supports larger drives (up to 64TB) and includes power-failure protection to prevent data corruption. Pros & Cons Windows 8.1 ISO download source that isn't Windows website 17 Jun 2021 — windows 81 vhd download link
Oracle’s official “VirtualBox Images” page sometimes has Windows 8.1 legacy VMs for developers (usually unactivated, require user licensing). Right-click This PC > Manage > Disk Management [1]
: Contains various official-sourced Windows 8.1 ISOs and some pre-built VM images uploaded by contributors. 4. How to Create Your Own VHD windows 81 vhd download link
To sum up: from Microsoft for consumers. The correct workflow is: