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The option indicating that the system fails to boot is a strong indicator of potential power supply unit issues. When a computer does not boot, it may suggest that it is not receiving adequate power to perform the startup sequence. This can happen if the power supply is malfunctioning, failing to provide stable voltage, or has completely stopped functioning. A power supply that is unable to deliver the necessary power can lead to a failure to initialize the motherboard and other critical components.

While issues like the computer making noise, display resolution lowering, or lost BIOS settings can lead to various problems, they do not directly point to a power supply issue. Noise might suggest a hardware failure but could stem from fans or hard drives. A low display resolution typically relates to problems with the graphics card or its drivers. Lost BIOS settings are often a sign of a depleted CMOS battery rather than a failing power supply. Therefore, the failure to boot is the most definitive sign indicating that the power supply unit may need to be replaced.