So I just built a pc and I keep getting this error Reboot and select proper boot device. I am very confused I have windows installed from a usb and whenever I plug in my hardrive it says no operating system found but when the usb is connected it says reboot and select proper boot device, and that is without the hard drive. I know the hard drives work because they appear in bios. Also, I had used these hard drives to boot from my old laptop and it went to windows and I tried resetting my pc so I wouldn't have all of the old files and things I had. While I was resetting it it said it had an error and then the operating system wasn't there. The USB is windows 7, the old operating system on the hard drive was windows 10 and I have two hard drives.