When a computer is turned on, it stays on the first screen of the main board due to a variety of reasons. The following are some possible reasons: Power supply problem: insufficient power supply or damage may cause the computer to stay on the first screen of the main board when it is turned on. You can check if the power supply is working properly and replace it with another power supply to determine if it is a power supply problem. 2. hardware failure: hardware failure may also cause the computer to stay on the first screen of the main board. You can check if the hardware is connected properly and if there are any obvious error codes or hardware faults. Motherboard problems: Motherboard failure may also cause the computer to stay on the first screen of the motherboard when it boots. You can check the motherboards for any obvious error codes or damaged components. 4. The boot sequence setting problem: Some computer boot sequence settings may cause the computer to stay on the first screen of the motherboards. You can change the boot sequence through the Windows boot settings or the BIOS settings. 5. Corrupted system files: Corrupted system files may also cause the computer to stay on the first screen of the main board when it is turned on. You can try to use the system repair software to repair the system files or reload the operating system. If the specific cause cannot be determined, it is recommended to seek professional technical support or further trouble-shooting.