HP Laptop LCD Flickering.

Hi, my laptop got into power ON issue due to power cable clip on the motherboard. I got another laptop with the same configuration other than the processor. I took my hard drive and placed it in the new one and noticed that my screen was flickering. I reported that to the hardware technician and he replaced my lcd with my previous one. but it didn't resolve the issue. then he change the board of my new laptop with the board of my previous laptop, still the issue didn't resolved. then he install new windows into my system and it looked perfectly fine but after an hour again flickering started. when my laptop is on DOS mode, nothing as such happens but when windows mode is On, flickering starts, so my hardware technician says that its not a hardware issue but software issue, but after done so many things, I am out of solutions now and need help in order to fix it.