Fix: Windows 8 ISO mount – “Couldn’t Mount File”

Since Windows 8 I quickly learned to appreciate the feature to mount an ISO file as a virtual drive via double-click without the need for any additional tools. However, Windows stubbornly refuses mounting specific ISO images.

Error description

Trying to mount an ISO image under Windows 8 or Windows 8.1 (via double-click or right-click > Mount), the following error message shows up:

ISO_ErrorCouldn’t Mount File – Sorry, there was a problem mounting the file.

This even occours on a recently installed system with the latest Windows 8.1 Update 1. Other tools (link WinRAR) don’t have any issue with the files.


There are two possibilities: The error occours with specific ISO files only or it does occur in general.

  • Some download managers write large files as sparse files which are not supported by Windows’ ISO mount feature (sparse files do have a “P” in the file properties under Details > Attributes). This can be fixed by simply copying (hence rewriting) the concerning ISO file: Drag the ISO with pressed CTRL key to e.g. the desktop, delete the original file and move the ISO back to it’s original place. Now the file is healed permanently and can be mounted without issues.
  • If the error does occur in general, there may is no appropriate free drive letter. Windows wants a letter after the harddisk partitions but before the first removable drive (e.g. card reader). This can be solved with Windows Disk Management: Right-click at the bottom left screen corner > Disk Management, then right-click in the bottom list at Removable > Change Drive Letter and Paths… and assign a letter somewhere higher in the alphabet.

Further reading


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