There is music on the desktop when the computer is turned on. Listen to it. If so, the system has started normally. Then the cable of the computer's internal display screen fell off, or the driving board burned, and the display screen needed to be repaired or replaced.
If you wait for a long time and still don't get the music on the desktop, the problem will be difficult to solve.
Hymns need to be checked step by step, such as memory, but normal fan operation means normal memory.
There is also a graphics card. You can try unplugging the external graphics card and integrating it with the motherboard.
If the cpu or south bridge is broken, after step-by-step investigation, go to the repair shop for repair.
I hope I can help you.