Originally Posted by rulezero
You check all the cables, especially the SATA? maybe its loose and caused the reboot and to not find the OS.
It was resolved by changing the boot order in the BIOS to check the primary hard drive first. The computer never had issues seeing the hard drive. I haven't had any issues since so I think if it was something like a loose cable, that wouldn't have fixed it.
I discovered a Trojan on my system yesterday evening so I am wondering if that may have been a factor. It's still strange though, how all of a sudden it didn't like the DVD-ROM drive being at top boot priority followed by my two hard drives.