To resolve this issue, both FAT32 partitions need to be removed from the disk and a new ISO must be created where no single file is larger than 4GB. The OSXRESERVED partition is hidden and unmounted, and Boot Camp Assistant cannot restore a disk that has multiple FAT32 partitions. To make matters even worse, the disk in the Mac is left in a state where it is difficult to revert back to a single partition. This file is required, so the whole process aborts. In step 3 above, the error message “An Error occurred while copying the Windows installation files” is shown because Boot Camp assistant cannot copy the install.wim to a FAT32 filesystem. Each new version of Windows increases the size of this file, and ISOs that contain more editions of Windows can be larger than other ISOs that contain less editions. So, here is where the problem resides: FAT32 cannot handle files greater than 4 GB. The install.wim contains all of the files for a vanilla copy of Windows 10 and is the largest file in the installer ISO. This is a large file (usually around 4 GB). Windows boots from the OSXRESERVED and shows the available editions of Windows from the install.wim file in the support folder on OSXRESERVED.

Sets the boot disk to the OSXRESERVED partition and reboots.

These files provide both the drivers needed when installing and the drivers that are installed post-install.

Copies the files from the WindowsSupport to the OSXRESERVED partition.

Copies all the files from the ISO that was specified at the start of the process by the user to the OSXRESERVED partition.

Creates 2 partitions, one where Windows will be installed (“BOOTCAMP”) and one where the installer files will reside (“OSXRESERVED”).

Download the Windows Support software from Apple for the current Mac.

To do this, it does the following operations: When Windows 10 is installed with Boot Camp Assistant, Boot Camp Assistant prepares the disk for installation. I have seen it a lot, since I do testing with ISO of Windows Enterprise downloaded from Microsoft that have been showing this problem. It didn’t seem to happen with all ISO so I investigated the issue, filed a bug with Apple, and figured out a workaround to the problem. In the last few months, people installing Windows on their Macs with Boot Camp Assistant have started seeing the message “An Error occurred while copying the Windows installation files” when using some Windows 10 ISO downloaded from Microsoft. WE HAVE LEFT THIS ARTICLE AND THE DOWNLOAD FOR HISTORICAL PURPOSES. NOTE: THIS UTILITY SHOULD NO LONGER BE NEEDED DUE TO APPLE UPDATING BOOT CAMP ASSISTANT TO USE EXFAT. Posted on Novemby Timothy Perfitt - Boot Camp Updates Using larger Windows 10 ISOs with Boot Camp Assistant

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