My HP Dv5-1125nr has a screen flickering problem

I have an HP Dv5-1125nr running windows vista that my friend gave me that I decided to take apart a couple years back to clean out the dust as it was causing the computer to overheat and shut off constantly. I took it apart, cleaned it out and put everything back together properly without any extra pieces or anything being broken. I used a guide to take it apart just to be sure. When I turned it on the computer would boot fine but the screen was flickering. A very bad flickering. I tried to find an example on YouTube but I couldn't so I uploaded my own. https://youtu.be/gGWFtNNDU7g At first I thought maybe I did something to the screen when I was taking it apart so I bought a new screen and put it on and nothing. The flickering still persisted. I hooked the laptop up to an external monitor with a VGA cable and it worked fine. Recently the VGA port stopped working as well. I hooked it up with HDMI and that worked for a little while but now that's not very reliable either. It takes me an hour to get the laptop to connect through it now. My next idea is to buy a whole new motherboard for it but I wanted to see I anyone had any other ideas before I drop that much money on this computer. Any help would be appreciated thanks.