hi, thanks for your reply The model is an HP 255, Win 10 what I eventually want to do is create a dual boot with Linux but at the moment I just want to be able to run it from a live usb so I want to be able to change the boot sequence to do this.
Press "Esc" or "F9" right away after the power ... Press "Esc" to open a menu that you can then pick your option from or "F9" which should be the boot option
the point is that then means if a single key isn't working for whatever reason you can still get into your system