I just recently started getting this message. Whenever I get it, if I just simply shut my computer off and start it right after it usually boots up like normal. I can't figure out what is going on. I've tried taking my computer apart and making sure my SATA drive is plugged in properly. I went into my BIOS and it says my SATA drive is first on boot. I went into my BIOS and one time it showed my external hard drive as the first boot, and SATA on the second, however when I unplugged my external it still went to the Reboot and Select Proper boot device screen. I checked my BIOS a few times so far and my SATA has showed up on the list as first every time except for that one time where my external was on it. I was hoping someone could suggest something to me to fix this issue. I don't want to have to keep restarting my computer to get it to boot right. I thought maybe I should try going to a restore point from a few weeks ago. Thought maybe an update may have messed something up.