“Missing Operating system” on Boot

ERROR Yikes.
When  playing with BIOS settings to try and use Graphics card + OnBoard (see previous post), I was curious to see if OnBoard would work on it’s own. So change one option to IDE, with no graphics card. At this point I had no monitor, possibly only on boot. I may have at some point used some form of Restore Default Settings. From this point forth it would not boot, but would just display “Missing Operating System”.

SOLVED: With more technical support we realised that the SATA configuration settings were something other than RAID, which this machine is on. After reverting this back to RAID the machine booted again.