I'm not sure what cause it, but now whenever I boot up my desktop, a message comes up that says "reboot and select proper boot device." I went to the BIOS Setup to see if my Boot priority had been changed. In the menu for priority, my hard drive doesn't even show up and there is no option to boot from hard drive. How do I fix this? Thanks.

Welcome to the forum.

Fistly, did you change anything inside the PC recently? This problem is usually caused by a reversed IDE cable or wrongly installed hard drive jumpers. Open the case and carefully check to see that you can actually hear the drive when you switch the PC on...it should whine then click into life. If not, the next best thing to do is take it to another PC and see if it will work there.

A system check randomly ran when I started it up this morning. It seems to have fixed the problem. I haven't changed anything inside the computer, but the problem seems to be fixed now, so no worries. Thank you.