Pc not booting up

The computer is an hp pavillion model 15-cb007ns. My brother didn't use it for a while because 'it worked like ****'. I decided to take a look at it. About a minute after pressing the power button the screen got an image that resembles the start of a very old movie(black background, smaller white rectangle in the middle and a countdown, obviously without the countdown). The image was extremely blurry and disappeared pretty quickly to just a black screen. About an hour/hour and a half later (we went out) the computer finally booted up. The screen was screwed up with glitched lines appearing everywhere and a white rectangle sometimes covering up part of the left side of the screen. Basically, the computer was unusable, so I thought that by changing the screen cable that issue will be solved, and I could take a look at the software side of things. Well today I booked an appointment at a computer repair shop to get the cable changed and decided to boot up the computer beforehand to not have the IT guy waiting an hour for it to boot up. I got the same screen after pressing the power button but the computer never booted up. I gave up waiting after about an hour, shut it off and tried turning it on again but this time I tried entering the bios settings (f10). The computer started beeping (high pitched, short, continuos). I powered it off and tried again with the same result. I then repeated that a third time while pressing the other f buttons but couldn't get the beep to go off again, including with f10(I tried a couple more times with just f10) . Now when powered on it doesn't even display the white image and just stays at a black screen. One interesting fact is that the keyboard lights still work perfectly. Any help is greatly appreciated