Do you have the GWX icon so that you can use it to check your machine's compatibility and have you created an external system image first as a fall back.
One thing to do first if you haven't already done it is to set the computer so that it will check the DVD and USB drives first before the HDD, as F2 and F12 no longer work in Win 10 - probably because of the speed it boots up, although you can get it to do that from within Win 10 - but that won't help if you can't get in.