Getting the real, untampered ISO is your first and most important step. Here's how to do it safely:
: If you require authentic 32-bit (x86) legacy versions (such as the legendary v15.2 or earlier), access the Hiren's BootCD PE Old Versions Page or browse the Hiren's BootCD Archive Gist for indexed direct download paths. hbcdpex86iso link
Ensure the file system is set to FAT32, and the partition scheme and target system type are set appropriately for your USB and system. Getting the real, untampered ISO is your first