Question : Problem: Intermittent "Operating System Not Found"

I'm getting an intermittent Operating System Not Found upon boot.  I have already replaced HDD (Old one had bad sectors also, so I assumed it was just a symptom of the failing hdd).  I get this error only about 1 in 10 times booting up, and have never been able to reproduce it twice in a row.  Any thoughts on what could cause this?  It's annoying!

Answer : Problem: Intermittent "Operating System Not Found"

If it occurs when the system is powered up, it can be a timing issue, when the drive is accessed for the OS before the drive is up to speed and ready to operate.