The problem is that their required download manager is setting the download file to be a sparse file as can be seen by the "P" attribute as explained here:
The download manager doing this is Akamia NetSession Client:
2013-12-18
Bug of the Day: Couldn't Mount File in Windows 8.1
If you download an .iso or a .vhd file from the Microsoft TechNet Evaluation Center and then try to mount it in Windows 8.1, you get:
The problem is that their required download manager is setting the download file to be a sparse file as can be seen by the "P" attribute as explained here:
The download manager doing this is Akamia NetSession Client:
If you make a copy of the file using Windows Explorer, the copy of the file is not a sparse file, and it is mountable. It is just not intuitive at all at first. I downloaded the iso file several times, thinking it was corrupt.
The problem is that their required download manager is setting the download file to be a sparse file as can be seen by the "P" attribute as explained here:
The download manager doing this is Akamia NetSession Client: