Monitor no signal only fan spin

Hello, I had a problem with my Dell desktop. While I was playing game, my moniot was stuck and keyboard was not working, only mouse can be moved. Then I pressed the bottom to turn the computer off. When I turned it on again, no monitor signal but the flash green light. The keyboard still not working, only mouse had its light. I noticed that only fan spinned.

I saw the old post and I tried many of them such as clear CMOS detached RAM and put it back, unplug power supply. But still not working.

Anyone has a any idear, thanks very much,

Sarin