Most modern systems are coming with UEFI as the default firmware. This is a good thing. However, there is a little problem. To install Windows 10 on a UEFI system, you need to create a bootable drive with the FAT32 file system. The FAT32 file system can only store files that are less than 4GB.
This may not be a problem for regular users. As of writing this, the Windows 10 default “install.wim” file is just barely under 4GB. However, if you are creating a custom image file with custom software and settings, that “install.wim” file can be massive. In those situations you can split the Install.wim file into multiple SWM files. This allows you to create a FAT32 formatted UEFI bootable drive without any hiccups.
Let’s take a look at two ways to split the install.wim file. The first method uses a third-party tool, and the second method uses the built-in Windows command. Follow the method of your choice.
Before proceeding, make sure that you have the custom “install.wim” file available. It’s being assumed you know how to create a bootable drive.
Use a Third-party Tool to Split Install.wim File
To split the install.wim file we are going to use a free and portable tool called GImageX. Download the tool from the official website and extract the contents to your desktop.
Open the extracted folder, go to the “x64” or “x84” folder depending on your system type and double-click on the EXE file. Being a portable tool, you don’t have to install it.
Once the tool is opened, go to the “Split” tab. Click on the “Browse” button under the Source WIM section, navigate to where the source “install.wim” file is located and open it.
Next, we need to select a destination. Click on the “Browse” button under the Destination SWM section, navigate to where you want to store the SWM files, name the file as “install.swm” and click Save. The path will automatically be added to the tool.
Under the Destination SWM section, select the split size. The tool lets you choose either 4GB or 600MB. Select either of the choices. In this case 600 MB is being selected for demonstration purposes.
Finally, click on the “Split” button. If you want to, select the “Check” checkbox under the Options section to verify the integrity of the split files.
As soon as you click on the button, the tool starts to split the install.wim file. Depending on the file size, it can take some time.
Once everything is done, the tool will show the “Image Split Successfully” message.
If you go to the destination folder, you will find the new numbered install.swm files.
Commands to Split Install.wim File
If you don’t like using a third-party tool, you can use the built-in DISM tool to split install.wim. All it takes is a single line command.
First, search for the command prompt in the Start menu, right-click on it and select the “Run as Administrator” option.
In the command prompt window execute the following command while replacing the source and destination path with the actual paths. In this case the source is located in the “J” drive, and the SWM files are being saved to the “H” drive.
By default, the command will split install.wim into 1GB files. You can customize the output file size by modifying the
/filesize parameter in MBs.
If the command is successful, it will show “The operation completed successfully” message.
Of course, you can also see the broken up install.wim files in the destination folder.
Once you are done splitting the install.wim file, you can either copy the SWM files to the bootable drive or use the WinPE Deployment tool to create a bootable drive. If you need assistance in creating the bootable drive with the split install.wim files, I recommend you take a look at this Microsoft doc.