My Toshiba Portage R930 won't boot. F2 comes up but not F8 for repair. I am currently running Windows 10. When trying to boot the screen shows a 1/2 cycle then repeats. When holding F8 then the power button I get a beep sound only. When I push Ctrl Alt Del the login window briefly appears. Other than that I can only look at F2 and am not sure what I am looking at.