After installing a new secondary hard drive in a Windows 10 desktop, the computer displayed the error message: No Operating System Found. What should the technician do NEXT?

When a computer displays the error message "No Operating System Found" after installing a new secondary hard drive, it's essential to check the boot order as the next step. The boot order tells the computer which drive to look at first when starting up. If the new hard drive has been added but is not configured properly in the boot sequence, the system may be trying to boot from the wrong drive, leading to the error message.

In this situation, by checking and potentially adjusting the boot order in the BIOS or UEFI settings, the technician can ensure that the primary drive, which contains the operating system, is listed first in the sequence. Once this adjustment is made, the system should boot normally, and the error should be resolved.

The other options, while potentially useful in different scenarios, do not address the immediate issue of the computer not recognizing the operating system due to boot configuration. Rebooting into safe mode wouldn't apply as you can't access the OS, formatting the new drive is unnecessary unless the drive is going to be used for storage and doesn't contain any required data, and performing Windows recovery is more complex than needed for this specific issue. Therefore, verifying the boot order is the most appropriate next step.