I recently wanted to install windows 10 on my HP15 laptop which comes with windows 8 pre installed. I tried all ways of disabling secure boot and enabling legacy boot so that i may be able to boot from a bootable USB flash but to no avail. I then went to command prompt and deleted all my gpt partitions but forgot to convert to MBR, so i'm now stuck. There is no OS in the laptop now and it cannot allow me to install any operating system. It brings an error of "Selected boot image did not authenticate. Press <Enter> to continue". I have tried almost everything including hardware reset but nothing is still working. Someone hook me up here coz this stuff is realy stressing me!