If you are getting the SC00009E No Valid Start Key error message, before you start by doing anything else, make sure you have disabled secure boot for your version of windows. Google that bit specifc for you device manufacturer, but its straight forward.
The quick way of checking if its on or off is:
'windows key' + R (or start menu > run)
type 'msinfo32'
Hit ok
Look up the secure boot line to see if its on or off.