No operating system found, then it is after I press space

When I power up my machine, after BIOS the computer beeps with the 'no operating system found, press any key to continue.'. I press a key, and the machine boots no problem. This happens even with only the boot drive in the machine.. I've tried it with the drive in several different SATA plugs. The drive is an SSD if that matters.

Anybody have any ideas?

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