Windows 10 installer files too big for USB flash drive? Here’s the fix

Microsoft has made Windows 10 version 2004 available to the developer community, a few weeks before its release to the overall public. Like many IT pros with a visible Studio (formerly MSDN) subscription, I downloaded the ISO file yesterday and set close to copy it to a bootable USB flash drive.

Normally, that’s an easy process: First, use the Recovery Media Creator to make a bootable USB flash drive; then double-click the Windows 10 v2004 ISO enter File Explorer to mount it as a virtual drive and drag the contents of the mounted drive to the bootable USB flash drive.

That option works fine once you download the Windows 10 installer files using the official Windows 10 Download page, because those files are packaged specifically to be used on USB flash drives. But that page only includes the newest official release. If you’re downloading an advance release, as I was, or if you would like the previous release, you’ll run into an old, familiar, and very annoying problem. rather than completing an easy drag-and-drop copy operation needless to say , File Explorer puts up this File overlarge error message:

Files larger than 4 GB won’t fit on a drive that’s formatted with FAT32

The reason for the error is simple: The Windows Imaging format (WIM) enter that download, which contains the compressed files that the Windows Setup program uses for installing the remake , may be a little over 4.5 GB in size, which is well beyond the 4 GB maximum file sizefor a USB flash drive formatted using the FAT32 filing system . That extra-large file would be fine for a drive formatted using NTFS, but modern UEFI-based hardware requires a FAT32 drive else for a clean install of Windows.

What’s an IT pro to do?

Well, you’ll just mount the ISO as a virtual drive and run Setup from within Windows. otherwise you could attach the ISO file as a virtual DVD drive during a virtual machine. otherwise you could use various deployment tools to manage the installation over a network.

But if you need the choice to run Setup from a bootable drive so you’ll do a totally clean install, you will need to leap through the subsequent command-line hoops to separate the WIM file into pieces that are under the 4 GB FAT32 size limit. Here’s how.

Step 1: Create a bootable recovery drive. On a PC that’s already running Windows 10, create a bootable flash drive using the Windows Recovery Media Creator (RecoveryDrive.exe). you will need a drive that’s a minimum of 8 GB in size. Don’t select the choice to copy system files to the recovery drive, and note that each one files on the drive are going to be erased when it’s formatted.

Use a USB flash drive that’s a minimum of 8 GB in size, and confirm to go away this check box unselected

Step 2: Mount the ISO file and replica it to an area drive. Open File Explorer and double-click the downloaded ISO file to mount it as a virtual drive. Leave that File Explorer window open and press Ctrl+N to open a replacement window. within the new window, create a folder on an area hard disc and replica the contents of the mounted drive from the opposite window thereto folder.

Step 3: Use the DISM command to separate the WIM file into multiple pieces. Open a prompt window as an Administrator and sort the subsequent command, 

substituting the name of the folder that you simply created in Step 2.
Dism /Split-Image /ImageFile:C:\folder_name\sources\install.wim /SWMFile:C:\folder_name\sources\install.swm /FileSize:3800

After the operation completes, check the contents of the Sources folder. you ought to see two new files, Install.swm and Install2.swm, alongside the first Install.wim. you’ll now safely delete the Install.wim file from the folder you created.

Step 4: Copy the installation files from your local folder to the bootable USB drive. Make sure you copy all the folders, as shown here. If you’re asked whether you want to replace files on the destination drive, say yes.

Drag of these files to the bootable flash drive; choose the choice to exchange files if prompted

This time, you should not receive that pesky File overlarge error. Windows Setup recognizes the 2 split files with the .SWM file name extensions and uses them to make the new installation.

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