Display problem. What happened to the nvidia 840m graphics card?

Question

Windows

After I disassembled/reassembled the laptop. This "distortion" has begun

Answer 1

If the video card had an open unprotected crystal, you may have chipped a corner when installing the radiator, due to which the damaged video processor began to produce artifacts.
Just in case, if you ask why there are no artifacts on Windows windows and the desktop - all this is generated on the CPU, the video card only displays the image on the screen. But in the case of rendering in games and three-dimensional applications, the image is created by the processor of the video card and therefore artifacts.