How to Create a Bootable Windows 10 Installation USB Drive Using Mac OS ISO

Creating a bootable Windows 10 installation USB drive is a relatively straightforward process, but there are a few hurdles that need to be overcome. One of the main issues you may face is the large file size of the install.wim file in the sources folder, which exceeds the 4GB limit of FAT32-formatted USB drives.

To begin with, you'll need to download the Windows 10 ISO from Microsoft's website. When downloading the ISO on a Mac, you should be able to select the '64-bit Download' option and wait for the file to complete its download.

Once the ISO has finished downloading, you can start preparing your USB drive. First, create a new folder on your desktop called 'sources'. Copy all files from the sources folder, except for the install.wim file, into this new folder. Then, copy all remaining files and folders from the original ISO to the USB drive using Finder.

However, you'll soon realize that the sources folder contains one large file: install.wim, which exceeds 4GB in size and won't fit on a FAT32-formatted USB drive. To overcome this, we can use a tool called Wimlib to split the install.wim file into two parts.

To do this, open Disk Utility on your Mac and choose to show all devices. Insert your USB drive and start Disk Utility. Select the USB drive from the list and click 'Erase' in the top-right menu. In the dialog box that appears, enter a name for the drive (e.g., WINUSB), select 'MS-DOS (FAT)' as the file system, and choose 'Master Boot Record' as the scheme.

After erasing the USB drive, you'll need to split the install.wim file using Wimlib. You can download Wimlib from its official website and follow the instructions to split the file into two parts.

Once the file has been split, you can copy all smaller files to the USB drive, leaving out the sources folder for now. After completing this step, your USB drive should be prepared.

Finally, click 'Erase' again in Disk Utility to complete the process. In the dialog box that appears, enter a name for the drive and select 'MS-DOS (FAT)' as the file system.

With these steps completed, you should now have a bootable Windows 10 installation USB drive that's ready to use.

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