(1) Check Power Supply Connections: (1.1) Ensure that all power supply cables are properly connected to the motherboard, CPU, GPU (if applicable), and other components. (1.2) Verify that the power supply switch (if present) is turned on. (2) Inspect the Power Supply: (2.1) Make sure the power supply is correctly rated for your computer's power requirements. (2.2) Check for any visible damage or burnt smells coming from the power supply. (3) Test the Power Supply: (3.1) Use a power supply tester to check if the power supply is providing the correct voltages. (3.2) Alternatively, if you have access to another working power supply, you could temporarily swap it in to see if the problem persists. (4) Check for Hardware Issues: (4.1) Disconnect all peripherals (external hard drives, printers, etc.) and remove any non-essential internal components (extra RAM sticks, additional drives, etc.) to see if the computer starts with a minimal configuration. (4.2) Reseat the RAM and any expansion cards (GPU, network...