The message may indicate that the PC cannot read the Operational System from your hard drive. I strongly recommend you to open BIOS and check if the hard drive is correctly recognized. Are we talking about a laptop or a desktop PC?
If the drive is not listed in BIOS, disconnect it and reconnect it. If it is a desktop PC, change SATA ports and cables. If you have the chance, connect it in another PC as a secondary storage drive and try to access it.
Let me know if there is any progress!