I don't know what happened here, but I was using a 256 gig M.2 SSD as a boot drive. Worked fine, and I never really had a problem with it until now. Today, I was using my computer for a couple hours, shut it off to go to the doctor, and came back. Now, my computer will only go to the loading Windows screen, for a brief second, then a black screen. I went into my BIOS to figure out what's going on, and I find that my SSD is no longer an option in my boot devices, but when I go to the tab with all storage devices, it's there. I've tried reseating everything (including CPU, GPU, RAM, etc.), removing memory sticks, clearing CMOS, etc. I'm at a loss here. I can provide pictures/videos if they're needed.