Bootable usb r not working to my computer

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Assuming the USB is actually 'bootable' then next you need to select the USB Drive as first priority boot device in the BIOS AND the USB port MUST be native; e.g. USB 3.0 ports are NOT native (yet). Further, as 'best practice' only use the native USB ports at the MOBO's I/O and NOT through a HUB or Case port(s).