TL;DR: How to make a bootable Windows 11 USB installer

The fix only. No explanation, no diagnosis. Read the full article if any of this does not match what you are seeing.

1. Use an 8 GB or larger USB drive with nothing on it you need. It will be erased.
2. Easiest route: on microsoft.com/software-download/windows11 choose "Create Windows 11 Installation Media", run the tool, pick "USB flash drive".
3. Manual route: download the ISO from the same page, then check its hash against the value Microsoft publishes for your language:

Get-FileHash -Algorithm SHA256 "$env:USERPROFILE\Downloads\<iso file name>.iso"

4. Format the drive GPT and FAT32 in diskpart (clean, convert gpt, create partition primary, format fs=fat32 quick, assign), mount the ISO and copy everything across.
5. If sources\install.wim is over 4 GB, copy everything except it, then split it:

robocopy D: E: /s /max:3800000000
Dism /Split-Image /ImageFile:D:\sources\install.wim /SWMFile:E:\sources\install.swm /FileSize:3800

6. Boot the target PC from the drive in UEFI mode using its boot menu key (often Esc, F10 or F12; it varies by vendor).

Triple-check the disk number in diskpart. clean wipes whatever disk is selected.

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