Do not use File Explorer format. Use the command line:
Assuming you have:
We will use native Windows commands (diskpart) and the legacy Microsoft utility bootsect.exe. You do not need shady third-party software. Do not use File Explorer format
Sometimes the Windows USB/DVD Download Tool refuses to write XP because it detects an “unsupported ISO.” Fear not – you can still use raw Microsoft command-line tools present in every Windows copy: Do not use File Explorer format
This method uses 100% Microsoft-sourced binaries—no third-party tools. Do not use File Explorer format