1. First, check whether the operating system has started when the computer is turned on. If the operating system crashes, blue screen or restarts automatically, it means that the partition table and hard disk master boot record are normal, and the failure causes such as partition table damage, hard disk master boot record damage and hard disk partition end flag loss have been eliminated. Then use the following methods for diagnosis.

2. First, start the computer in safe mode to see if it can be started. If it can't start, it may be infected with a virus, lost system files, damaged operating system, damaged hard disk, hardware device conflict or hardware problems. Go to step 4. If the safe mode can be started, it may be that the hardware driver is incompatible with the system, the operating system has a problem or a virus infection.

3. Then run the antivirus software. If there is a virus, it may be caused by it. Restart the computer after antivirus. If it is not normal, you need to reinstall the operating system.