It surely is a hardware problem. If changing the cable and the screen don't help, it's the motherboard and that most often is quite expensive to replace.
If you feel it's software, go back to factory conditons.
i have old HP Elitebook 8560p laptop that have problem with showing image on laptop screen. When i connect laptop to external monitor it's working. I tried to update, delete old graphics card drivers but sometimes i get image on my laptop LCD and most of the time i don't get the image(only on external monitor). So my question is, if i need to replace LCD screen, display cable or there is problem with graphics card on the motherboard?
Once i got stripes on my LCD and after that laptop restarts saying that he run on some problems, something about VIDEO error.
What do you suggest to me? Is this hardware problem or something about the software?