You need a USB drive you can boot a PC from to install Windows 11: a clean install, a reinstall, a new PC, or a rebuild after a failed disk. This article uses only what Microsoft supplies: the Windows 11 Installation Media creation tool, or the Windows 11 ISO that Microsoft publishes plus Windows’ own tools (diskpart, robocopy, DISM). It does not use or recommend any third-party tool.
This erases the USB drive. Microsoft’s download page says “Any content on the flash drive will be deleted.” Copy anything you need off it first, and check you have picked the right drive before you confirm anything. The same goes for the PC you install onto: a clean install wipes the partitions you delete.
Applies to: building the drive on a Windows 10 or 11 PC, installing 64-bit (x64) Windows 11 on the target PC. Microsoft’s tool and ISO on that page are for x64; Arm64 ISOs are offered on a separate Microsoft page and the creation tool does not support Arm-based PCs. Run the commands in an elevated (Run as administrator) PowerShell or Command Prompt.
What is going on
A Windows installer on USB is a drive with the contents of the Windows installation image on it, set up so the PC’s firmware can boot it. Microsoft gives you two ways to get there:
- The Installation Media creation tool. It downloads Windows, formats the drive and copies everything for you. It is the right choice most of the time.
- The manual method. You download the ISO yourself, verify it, format the drive and copy the files. You need this when you want to check the image first, keep one ISO for several drives, build on a PC that has no internet, or the tool will not run.
The one trap in the manual method is a size limit. The drive has to be FAT32 so UEFI firmware can boot it, and FAT32 cannot hold a single file over 4 GB. The Windows image sources\install.wim is often larger than that, so it has to be split into smaller .swm files, which Setup reads automatically.
Before you start / check first
1. The drive
Microsoft’s download page asks for a USB flash drive of at least 8 GB. If you build by hand, note that the FAT32 file system on a Windows-formatted volume tops out at a 32 GB partition: Microsoft’s WinPE documentation says FAT32 has “a maximum partition size of 32GB” and that a larger key must be formatted to use only 32 GB. A new 8 to 32 GB drive avoids the question.
2. Will the target PC take Windows 11?
Building the drive does not check the PC you will install onto. Microsoft’s Windows 11 requirements page lists the minimums:
| Item | Minimum |
|---|---|
| Processor | 1 GHz or faster, 2 or more cores, compatible 64-bit processor or SoC |
| Memory | 4 GB |
| Storage | 64 GB or more available |
| System firmware | UEFI, Secure Boot capable |
| TPM | Trusted Platform Module (TPM) version 2.0 |
| Graphics | DirectX 12 or later with a WDDM 2.0 driver |
| Display | 720p, 9 inches or larger, 8 bits per colour channel |
| Internet | Needed for updates and some features. Windows 11 Home requires an internet connection and a Microsoft account to complete first-time setup |
The download page also says installing Windows 11 on a PC that does not meet the minimum system requirements is not recommended. This article does not cover ways around the requirements. On the target PC you can check the TPM version by running tpm.msc (look for Specification Version 2.0) and the Secure Boot state with Confirm-SecureBootUEFI in an elevated PowerShell. If TPM is switched off, firmware settings may call it TPM, PTT or fTPM [UNCONFIRMED: those vendor setting names are common but vary, check the PC maker’s documentation].
3. Internet and licence
Both Microsoft methods need an internet connection on the PC where you build the drive, and the tool needs administrator rights. You need a licence to install Windows 11. Microsoft’s support page says a 25-character product key may be asked for, a digital licence does not need one, and a key embedded in the device firmware that matches the edition is applied automatically.
Why this works
UEFI firmware boots from a FAT file system on a GPT disk by looking for a boot loader in the EFI folder, and Windows 11 requires UEFI firmware. A drive formatted GPT and FAT32 with the full contents of the Windows ISO on it is therefore a bootable installer. The only thing FAT32 cannot hold is a file over 4 GB, which is what splitting install.wim solves. The creation tool does all of this for you.
The fix
Method A. The Windows 11 Installation Media creation tool
- On a working Windows PC, open Microsoft’s download page,
https://www.microsoft.com/software-download/windows11. - Under Create Windows 11 Installation Media, select Download Now. This downloads
MediaCreationTool.exe. - Plug in the USB drive. Run the tool as administrator and accept the licence terms.
- Choose language, edition and architecture. If you are building for another PC, untick Use the recommended options for this PC so you can choose them [UNCONFIRMED: this wording is from Microsoft Q&A answers, not Microsoft’s support page, and the exact screens can change between tool versions].
- Choose USB flash drive, select your drive and select Next. Wait while it downloads Windows and writes the drive. Microsoft says the tool needs a reliable internet connection and that download time depends on its speed.
- The same tool can instead create an ISO file, which Microsoft’s support page mentions for virtual machines and for burning to a DVD.
Use a blank drive. Do not copy the ISO file onto the drive as an alternative: a bootable installer needs the extracted contents, not the ISO as a file.
Method B. Manual: download, verify, format, copy
1. Download the ISO. On the same download page, use Download Windows 11 Disk Image (ISO) for x64 devices, choose Windows 11 (multi-edition ISO), pick the language, and download the 64-bit file. Microsoft describes it as a multi-edition ISO that uses your product key to unlock the correct edition. The language must match the language you want during installation.
2. Check the SHA-256 hash. The same page publishes a SHA-256 value for each language. Compute the hash of your download and compare it with the one in Microsoft’s table for your language and architecture. Get-FileHash uses SHA256 by default, and the algorithm is stated here only to be explicit:
Get-FileHash -Algorithm SHA256 "$env:USERPROFILE\Downloads\<iso file name>.iso"The output has an Algorithm, a Hash and a Path. Compare the Hash with Microsoft’s value character by character, or let PowerShell do it:
(Get-FileHash -Algorithm SHA256 "$env:USERPROFILE\Downloads\<iso file name>.iso").Hash -eq "<paste the value from Microsoft's table>"True means the file is intact and unmodified. If it is False, delete the file and download it again, and check you used the row for the right language and for x64. Do not use an ISO whose hash does not match.
3. Format the USB drive as GPT and FAT32. Plug in the drive. Use diskpart from an elevated prompt. The clean and convert gpt steps are from Microsoft’s documentation on partition styles, and the partition and format commands follow the examples in Microsoft’s WinPE documentation.
diskpart
list disk
select disk 1
clean
convert gpt
create partition primary
format fs=fat32 quick label="WIN11"
assign
exitCheck the disk number. Replace 1 with the number of the USB drive shown by list disk, matching it by size. clean removes all partitions and data from the selected disk. If you pick your system disk, you wipe your PC. Stop and re-check if you are not certain. If the drive is over 32 GB, add size=32768 to create partition primary so FAT32 will accept it [UNCONFIRMED: the size value is arithmetic from Microsoft’s 32 GB statement, not a documented command line].
Microsoft’s page for making a flash drive by hand also marks the partition active, so the drive boots both BIOS-based and UEFI-based PCs. A GPT drive is for UEFI boot, which is what Windows 11 needs, so that step does not apply here [UNCONFIRMED: Microsoft’s page does not say this in so many words].
4. Mount the ISO and copy its contents. In File Explorer, double-click the ISO to mount it as a virtual DVD (or right-click it and choose Mount). Note the drive letter, here D:, and the letter of your USB drive, here E:. First see whether the image is over the FAT32 limit:
(Get-Item D:\sources\install.wim).Length / 1GBIf it is under 4 GB, copy everything:
robocopy D:\ E:\ /EIf it is 4 GB or more, use Microsoft’s two-step method. Copy everything except the image, then split the image onto the drive:
robocopy D: E: /s /max:3800000000
Dism /Split-Image /ImageFile:D:\sources\install.wim /SWMFile:E:\sources\install.swm /FileSize:3800The first command skips any file larger than about 3.8 GB (so it leaves out install.wim), and the second splits install.wim into parts of up to 3,800 MB with the first named install.swm, followed by numbered parts [UNCONFIRMED: the exact names of the later parts are not stated on the Microsoft page]. Microsoft notes that Windows Setup installs from them automatically so long as the first is named install.swm. Do not rename them, and do not also copy the original install.wim. If you used the tool in Method A, none of this is needed.
UEFI, legacy BIOS and Secure Boot
- UEFI. Windows 11 requires UEFI firmware, so boot the installer in UEFI mode. Microsoft’s partition-style page explains the error “Windows cannot be installed to this disk. The selected disk is not of the GPT partition style”: it appears when the PC is booted in UEFI mode but the internal disk is not GPT. On a clean install, deleting all partitions on that disk in Setup’s Custom screen lets Setup recreate it as GPT. Setup will not make that change until you delete the partitions, and that erases the disk.
- Legacy BIOS / CSM. A BIOS-compatible boot needs an MBR disk. It is not the Windows 11 path and is not covered here. If a PC boots the drive in legacy mode, switch the firmware to UEFI and boot the USB entry that starts with “UEFI”.
- Secure Boot. Windows 11 needs a Secure Boot capable PC, and you should install with it on. Microsoft’s download page notes that if the USB drive does not show up as a boot option, you may need to turn Secure Boot off temporarily in the BIOS/UEFI settings, and the manufacturer can tell you how. Turn it back on afterwards.
- TPM 2.0. Required for Windows 11 per Microsoft’s requirements page. Microsoft says installing on a PC that does not meet the requirements is not recommended. The installer media is the same either way, so check the PC first, as in the “check first” section.
Boot the target PC from the drive
- Plug the USB drive into the target PC and switch it on.
- Press the key for the boot-device menu straight away. Microsoft’s documentation gives Esc, F10 and F12 as examples, and says to consult the manufacturer if it does not work. The key differs by vendor (F2 and Del are also common for the firmware setup screen, which has the boot order if there is no boot menu). Look for a prompt on the logo screen, or check the PC maker’s support pages.
- Choose the entry for the USB drive, preferably the one marked UEFI. Windows Setup starts.
- Choose language and keyboard, select Install Windows 11, and when asked for the installation type, select Custom. Select and delete the old partitions on the correct disk only (Microsoft cautions about this on PCs with several drives), select the unallocated space and select Next.
- When it finishes and restarts, remove the USB drive. If you changed the boot order, set it back so the internal drive boots normally.
Building and installing offline (air-gapped)
Both Microsoft methods need internet at the point of building or downloading, so for a network with no internet access, split the job:
- On a PC with internet, download the ISO from Microsoft and verify the SHA-256 hash against Microsoft’s value, as above.
- Move the ISO to the offline network using whatever removable media your policy allows. Run
Get-FileHashagain on the offline side and compare with the same Microsoft value, because a copy can be corrupted or changed in transit. - On an offline Windows PC, build the drive with Method B. The tool in Method A needs internet, so it is not an option there.
- Download in advance, on the connected PC, anything the freshly installed PC will need and cannot fetch: the network and storage drivers from the PC manufacturer, and the latest cumulative update from the Microsoft Update Catalog, then carry them across the same way. If setup stops at a screen that wants a network connection and the PC has no driver for its network adapter, you will need a driver on separate media.
- Windows 11 Home requires an internet connection and a Microsoft account to finish first-time setup, according to Microsoft’s requirements page, so it is a poor fit for an air-gapped PC. Use an edition and licensing route suited to your network [UNCONFIRMED: how to complete first-time setup on an offline PC is not covered here, and the workarounds in circulation are not documented by Microsoft].
Verification
- Open the USB drive in File Explorer. A working installer has
boot,efiandsourcesfolders andsetup.exein the root. - In
sourcesyou seeinstall.wim(under 4 GB) orinstall.swmand its numbered parts. You should not have both. - The drive appears as a UEFI boot choice on the target PC, and Windows Setup starts with the language screen.
- For Method B, the hash you computed matched Microsoft’s value for your language.
Notes
- Only Microsoft tools here. Third-party drive-writing tools are outside this site’s rules for recommendations, so none is covered. If the creation tool fails, use Method B.
- Keep media current. Rebuild the drive when Microsoft releases a new Windows 11 version, rather than reusing an old one, and re-verify the hash each time. The download page names the current release.
- Back up first. Back up the PC’s data before you reinstall. Microsoft’s support page tells you to back up your files before installing or reinstalling Windows.
- Drivers. After installing, check the PC manufacturer’s site for drivers, as Microsoft’s download page suggests.
- Sources: Windows 11 download (https://www.microsoft.com/software-download/windows11), Create installation media for Windows (https://support.microsoft.com/windows/create-installation-media-for-windows-99a58364-8c02-206f-aa6f-40c3b507420d), Windows 11 requirements (https://learn.microsoft.com/windows/whats-new/windows-11-requirements), Install Windows from a flash drive (https://learn.microsoft.com/windows-hardware/manufacture/desktop/install-windows-from-a-usb-flash-drive), Installing using the MBR or GPT partition style (https://learn.microsoft.com/windows-hardware/manufacture/desktop/windows-setup-installing-using-the-mbr-or-gpt-partition-style), WinPE: store or split images using a single USB drive (https://learn.microsoft.com/windows-hardware/manufacture/desktop/winpe–use-a-single-usb-key-for-winpe-and-a-wim-file—wim), Get-FileHash (https://learn.microsoft.com/powershell/module/microsoft.powershell.utility/get-filehash).
Drive will not boot, or Setup will not start? Post the PC model, what you built the drive with and what you see on screen in The Patch Panel and we will work through it. The best answer earns points on Top of the Stack.