The computer won't start, and the monitor has no signal. I usually check like this. I don't know where the specific problem is now, and there is no alarm. Let's consider the simplest problem first, such as the memory stick is loose, or the motherboard can't recognize the memory because of gold finger oxidation. At this time, unplug the memory module, wipe it clean and insert it into the boot computer. This usually solves the problem. If not, if you have a discrete graphics card, wipe your golden finger after unplugging it. If the motherboard has an integrated vga interface, you can use the motherboard's graphics card interface. After judging the problem, plug in the graphics card. Don't panic if the memory graphics card can't solve the problem. You can remove the coms battery from the motherboard, cut off the power supply and install it in a few minutes. Sometimes, due to the change of hardware, the configuration change of coms may also cause the computer to fail to boot. If all this fails, we should consider the problem of motherboard or cpu. First, check whether the power supply is normal. The computer can't enter the system when it is turned on. There are two situations: there is a hardware problem in the self-test, and the self-test cannot enter the desktop, which is a system or driver problem. First, the self-check can pass, but it can't get into the desktop. It belongs to the problem of operating system or driver: why can't the computer enter the desktop normally or crash the blue screen after repeated restart? In the case of virus removal, it is generally because the GHOST version or other modified versions of the operating system are installed, and a large number of drivers that are not suitable for your hardware devices are integrated in advance, resulting in the system being unable to correctly identify and load the necessary hardware devices. This error can be corrected by downloading the operating system of the original image installation version and installing all drivers certified by Microsoft WHQL. If you don't want to reinstall, you can try to boot F8 into safe mode, uninstall the driver whose hardware device is incompatible (that is, right-click the device in the device manager) & Attribute > No > Digital Signature Program >: the driver of Microsoft Windows hardware compatible publisher), and reinstall the downloaded driver (WHQL) after automatically identifying the hardware device at startup. Then restart the computer again to see if there is any improvement. Then there is the software with duplicate functions in the system, which causes conflicts (for example, two or more software killers and firewalls are installed, and advertisements are blocked). If it is confirmed that it is not a system or software problem, you need to test the hardware in the following order: first, the memory is the most likely, then the CPU, then the hard disk, and finally the graphics card, and the motherboard is basically not blue. In addition, check whether the machine is overheated due to poor heat dissipation (if it is, a stronger radiator must be installed, heat dissipation silicone grease must be repainted, and high-power fans must be replaced). Check whether the top of the motherboard capacitor is convex (if convex, it must be replaced immediately). Also check whether the output voltage is unstable due to insufficient power supply of the chassis (if so, it must be replaced immediately). If there is no "drip" sound, it must be a hardware failure. It is necessary to make a preliminary judgment on the alarm sound of small horn (buzzer) in order to narrow the scope of hardware failure. Please refer to your motherboard manual for the specific meaning of starting the alarm sound. 2. If the self-test fails, it must be a hardware failure: after the computer is turned on, there is no "click". Why? Self-check after the computer starts, however, if you don't hear the ticking sound, it must be a hardware failure. The following aspects need to be excluded and checked: 1. The system time can't be dBIOSplayed and saved correctly, which is caused by insufficient battery power on the motherboard. Replace the new motherboard battery, and press the DEL key to start the computer and reset the correct system time. 2. Check whether the motherboard capacitor is bulging or leaking. If so, you should go to a professional computer maintenance place to replace the motherboard capacitor. 3. Unplug the memory module, wipe the golden finger with rubber, and then insert it back into the memory slot. 4. Plug all the hardware and connecting wires firmly again to avoid virtual connection. 5. Start it once when the chassis is opened to see if the fan works normally. 6. Check whether the power supply of the chassis is insufficient. If there is a replacement power supply at hand, try to replace it. 7. Whether there is a hard disk failure. Enter the BIOS and see if you can recognize the hard disk. 8. There is no signal on the display. Check the connection of the display part. The black screen or flower screen of the monitor may be the problem of the graphics card or the monitor itself. 9. Make a preliminary judgment according to the alarm sound of the small horn (buzzer) of the boot chassis combined with your specific BIOS to narrow down the scope of the problem. Please refer to your motherboard manual for the meaning of specific startup alarm sounds. 10. That's all I can think of for the time being, other components.