When troubleshooting a non-responsive computer, what would be a critical first step?

In the context of troubleshooting a non-responsive computer, checking for power is a critical first step because power is the fundamental requirement for all components to function. Without power, no tests or further troubleshooting steps can yield any results, as the system will not be operational at all.

Confirming that the computer is receiving power helps to identify whether the issue lies with the power supply, the power connection, or perhaps even an electrical outlet. Only after ensuring that power is present and functioning can the technician move on to inspecting other components like the motherboard, operating system, or RAM. If the computer is entirely unresponsive, focusing on more complex parts like reinstalling the operating system or replacing hardware is premature and may not address the root cause of the problem.