If you want to install a new OS, you have to download it onto a flash drive and then enter a pre-startup mode called BIOS. Then you select which drive you want to boot from. The flash drive, provided you have it inserted, will show up in the drive list. If a computer has a snapdragon or ARM processor, the pre-installed drive is the only drive that will show up in BIOS. A bootable media flash drive will not show up in BIOS.
