Why is checking the power supply connection important if a computer does not power on?

Checking the power supply connection is crucial because it directly verifies whether the computer is receiving power. Without a stable and effective power supply, the entire system will be unable to operate, leading to a situation where the computer does not power on. Ensuring that connections are secure can identify issues such as loose wires, faulty power cables, or problems with the power outlet itself. These checks are fundamental before troubleshooting other components, as no other diagnostic steps can be productive without power reaching the system.

The other choices are related to different aspects of computer functionality but do not address the immediate necessity of ensuring power is supplied to the computer. For instance, guaranteeing hardware upgrades and enhancing data storage capabilities pertain to system performance and capabilities rather than the basic operational requirement. Ensuring the functioning of external devices, while important, does not influence whether the internal hardware powers on, as it is primarily the internal power supply that needs to be verified first.