I am trying to fix a laptop for my dad's friend It's an ASUS K601. When I boot up it says "Missing Operating system. I know there is an OS on the drive because I took it out and backed her files up onto my computer. The boot order in the bios is 1 cd rom 2 removable device 3 hard drive 4 network. The thing is when I try and put the windows disc it still does the same thing I also tried a windows boot usb and linux boot usb it all doesn't matter it still says missing operating system. I know the usb drives boot and the windows dvd work in other computers. I tried as other forums suggested and made sure nothing was inserted into any removable drive that the computer may try to boot from but it still says that same message.