Lifted from the middle of a set of instructions for doing a completely clean install of Windows 10, using Rufus to create the bootable USB drive using the Win10 ISO file. The steps are the same regardless of the ISO file being used, though the answer to the MBR versus GPT part is not as important if you're not installing the operating system but just booting from a drive that contains a tool or tools.
Use (or a similar utility of your choosing) to burn the ISO to a flash drive to create bootable media. The following lettered steps presume you’re using Rufus. Attach your flash drive and run Rufus. In the first dropdown box:
a) If you know your machine is newer hardware that uses UEFI as opposed to BIOS, select GPT partition scheme for UEFI. If the machine originally came with Windows 8 or Windows 10 this is definitely the choice to make.
b) If you know your machine is older and uses BIOS, or are uncertain as to whether you have BIOS or UEFI, select MBR partition scheme for UEFI or BIOS. Virtually all machines that came with Windows 7 (and earlier Windows) were produced with BIOS and use MBR partitioning.
Leave the other checkboxes checked or unchecked with their defaults.
4. Find the Create a bootable disc using checkbox and make sure that the option ISO image is selected from the dropdown next to it. Just beyond that dropdown is the Click to select an image . . . button. Activate it and you will be presented with the standard Windows browse dialog that lets you locate and select the Windows 10 ISO file from wherever you saved it.
5. Activate the Start button. The ISO image will now be burned to the flash drive as bootable.--
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
If you remove all the homosexuals and homosexual influences from what is generally regarded as American culture, you are pretty much left with Let's Make a Deal.~ Fran Lebowitz