This is currently the only official version of Windows 8.1 still hosted directly by Microsoft. It is provided as an evaluation ISO that you can mount as a virtual disk. Evaluation (180-day trial) Source: Official Microsoft Download Center
Because retail ISOs and VHDs are no longer on Microsoft's primary download pages, community-maintained archives on the Internet Archive are the primary way to find original "Official from Microsoft" files. Download Link Windows 8.1 Home/Pro Multi-Language: Download Link Windows 8.1 Enterprise Preview: Download Link 3. Creating Your Own VHD from an ISO windows 81 vhd download link
ISO (Can be used to install onto a newly created VHD) 2. Verified Internet Archive Links This is currently the only official version of Windows 8
: Right-click 'This PC' > 'Manage' > 'Disk Management'. Download Link Windows 8
: Right-click the new disk, select 'Initialize Disk', and choose the MBR partition style for broad compatibility.