A technician is called to an office where the computer is randomly rebooting. Which component would most likely cause this issue?

The power supply is the most likely component to cause a computer to randomly reboot. The power supply unit (PSU) is responsible for providing stable and adequate power to all the components within the computer. If the PSU is faulty or failing, it may not deliver enough power consistently, leading to intermittent failures and causing the system to reboot without warning. This can happen due to issues such as voltage fluctuations or inadequate wattage to support the hardware being used.

When considering the other components, while RAM can certainly lead to system instability if defective, it typically results in crashes or blue screens rather than random reboots. A hard drive failure generally results in data loss or system errors rather than abrupt reboots, and while a cooling fan's malfunction can lead to overheating that might cause shutdowns, it is less common for it to cause random reboots. Therefore, the power supply stands out as the most likely culprit for the symptoms described.