Can't mound ISO files after windows update.

Disk defagmenters do not always manage to defragment all individual files, especially when the files are multi-GB ones.

Windows defrag rarely can defrag large files in a single pass - because when Windows is running, many files are open and not able to be moved, defragmented or deleted - interfering with the consolidation of a large file that may be fragmented by the intercalation of active files.

A boot-time defragmenter will defrag all files usually because Windows has not loaded yet and the majority of files are not opened.

Puran Defrag is one such example and also can defragment individual files on demand from the right-click menu.

Individual file defragmenters are also available from Neosmart and are used in the EasyBCD utility for defragmenting ISO files and VHDs:

From: EasyBCD

UltraDefrag

UltraDefrag is an excellent individual file defragment utility that can be used to quickly group all clusters of a single file. EasyBCD relies on this feature to prepare disk images for booting.
The following files in the EasyBCD distribution are derived from this package and governed by its license:

• bin/udefrag.dll
• bin/udefrag.exe
• bin/udefrag-kernel.dll
• bin/zenwinx.dll

Site: http://ultradefrag.sourceforge.net/
License: GPL v2
Source Code: ultradefrag-4.4.0.src.7z

Another defragmenter that can defrag individual files is Contig from Microsoft Sysinternals:

Contig

Sounds your issue is related to file permissions caused by the latest update.

The system does not have the correct permissions to access the images. As copying the files helps solve the issue, make a copy of any of the non working ISOs and then compare permissions on both. You should see some differences. For instance instead of seeing the System "user" or Administrators "group" as one of the entries in the security tab, you instead see a GUID (a long name consisting of numbers and letters separated by dashes). This means that that particular user/group with that particular GUID does not exist in your system anymore. This issue is caused by bad update/migration of the registry values during the windows update process.

This is a common issue that has happened to me multiple times when updating the system to latest builds/cumulative updates.

Of course the issue could be related to something completely different too.

black said:

Thought of that, it's something has to do with security preventing me from accessing those files.
I missed with permissions, no matter what change I do there, it didn't work.
But I see that it listed on Microsoft site by other users with certain update, I'm almost certain it's an update issue.
Since my update include that "certain update" causing the problem, but can't be removed since I installed my updates as one package.

Going to wait for another update, hopefully it will fix the problem, otherwise I will roll to older updates and remove this one.

Thank you for the reply :)

This issue can be manually fixed, but it's tricky. You need FULL permissions for SYSTEM group for your non working files. Those permissions can not be edited in GUI mode. You need to do this using Powershell or CMD.

Easier is to revert the update and see if it helped and then try to update the system to latest cumulative update, which should be newer than the one that caused the error for you.