I have a Lenovo 100s and I reset to factory settings and all I get now is a blue screen with. No bootable device press any key

You might want to try entering bios and click defaults someone may have changed the settings of BIOS from secure boot to Legacy support no secure boot and reinstalling the operating system won't do you a bit of good until you default your bios and save if that doesn't help you you better take your computer in and have them put a new operating system on it