So I went and got myself a new SSD drive and I installed it and everything worked perfectly fine. After shutting down and starting up the PC again, suddenly I get this "Reboot and select proper boot device" message. So I wondered if the problem was on the new SSD so I unplugged it and the computer booted again. A bit later, I tried to plug the SSD in again and it suddenly booted but after shutting it down it didnt. Did that 2 or 3 times but now Im sick of having to unplug, and plugging it in back and forth... Anyone who has ever encountered this problem?