Insert your flash drive into a working computer.
An ISO file is just a disk image; you cannot simply copy it onto a thumb drive. You must "burn" it to make it bootable. how to install windows 7 from iso file
Select Custom (advanced) . This is necessary for a clean install from an ISO. Insert your flash drive into a working computer
If the computer boots straight to your old Windows or gives an error, restart and enter the BIOS/UEFI settings (usually F2 or Del) and change the "Boot Order" so USB is first. how to install windows 7 from iso file
To install the OS, you must tell your computer to boot from the USB drive instead of the hard drive.