Did you check out the tiny lid switch? Sometime they go bad, or stick. I suspect that is not the problem, but it is the first place to start.
Since you see numbers counting, I guess it must be the Basic Input Output System (BIOS) doing a Power On Self Test (POST). Normally, systems would be set to skip this. So the question is, why is the POST counting your Random Access Memory (RAM)?
Either someone set it to count the RAM (disabled a quick-boot option in the BIOS), or the system recognized a problem, and is trying to resolve it.
Next, I would try setting the BIOS to defaults. Watch the screen when it starts, to find out how to enter the BIOS Setup (usually the Delete key will work, but commonly an F-key).
If your external screen didn't work, I would say to test your RAM, but it does... There is a F-key on many laptops for blanking the screen, but it won't usually stay blank... And it wouldn't be a driver, since the screen blanks before the Operating System is given control...
Get a really bright light, and shine it at an angle on the screen (with the external monitor unplugged). Can you see see a faint image?