So yesterday I was on my computer and it was working perfectly fine and I downloaded Modern Warfare. Today when I started up my computer I was greeted by a black screen saying Operating System not found. I have 2 storage devices, an NVMe which is screwed onto the motherboard and it is has Windows 10 on it, and a HDD which is connected by a cable. It said try disconnecting any drive that doesn’t have the operating system, so I tried unplugging the HDD from the motherboard and the power supply. Once I did that, I turned it on and it said something about reconnecting a drive. I tried replugging it in and it gave me the same problem as the first time. Any ideas or help would be appreciated.