I did a install of windows 10 that a friend had on a usb drive. after a couple of months i decided i wanted to go back to win 8, that came with my laptop. i was following the directions in windows 10. when my laptop restarted it has files missing. now it want let me do anything.IT SAYS the screen is locked in windows 10, i can not get into the registry to unlock cause i can not get back into windows 10. I need to format the hard-drive how do i format the HD? I guess that is what i need to do!? I ordered a flash drive from ASUS to reinstall windows 8, i can not do anything. i change in the bios, to start with dvd drive, again one of the files in there shows to be missing to change it. there is supposed to be a file called "UEFI: TOSHIBA MSFT NORB PMAP", (NOT THERE). SO I DONT KNOW WHAT TO DO about this mess except to format the drive and reinstall with the recovery disk i bought from ASUS for $45. i have a $800 laptop and a $45 flash drive packed away in the closet. Can anybody help please?