Hi I have a dell laptop that beeps 8 times, 6 then pause then twice more, and then it has a black screen and nothing happens. It wont boot to windows , it did once, I did a LCD Test By holding "D" and all colours are solid and finally I connected an external monitor that was using previously with the laptop as it has good colours and resolution and when i connect it i tried both VGA And HDMI It says no video input so nothing shows up could you tell me the problem like if its ram or something inside BTW I replaced the CMOS Battery
Eight beeps means the screen isn't detected -- six, which could be the cause of that one - means the video chip has failed. If you're seeing nothing on an external screen, the video chip is the cause. Since it has failed, the mainboard will need to be replaced.
If you need to access the hard drive, you can remove it and install it into an external case -- attach to a working system by USB and copy your data.
The boards aren't inordinately expensive to replace if you can do the job yourself: