No boot device found after disabling legacy mode from BIOS

I am using HP 15-n215tu. I want to install windows 8 in UEFI mode currently it is ruing on legacy mode. I tried to update BIOS but after update asap it restarts again it shifts to legacy mode. So, I switched to USB install but after disabling legacy mode from BIOS it restarts again and says no OS installed on hard disk. After that I went to boot from devices(perssing F9) but it does not show any boot device and later on when i checked into BIOS in UEFI mode it shows no INTERNAL HARD DISK but below it there is legacy mode which shows INTERNAL HARD DISK. I have created USB using rufus and read many tutorials but nothing hlped.