I have this Compaq 6510b laptop that will not start up. When I hit the power button the fans turn on but the monitor acts like it was never attached. I have had this issue with hp laptops in the past, and the simple solution was to open the screen all the way before hitting the power button, only then would it turn on. At one point I had to do this, but now it doesn't matter the angle of the screen, it will not turn on.

The second I hit the power button, I have to hold it down to shut it off (normally I would only have to press it)
The power light turns on (green) and stays on, and the Drive light, blinks amber once before entering this state.
I removed the hard drive and put it into another similar model and it worked just fine.
The keyboard bezel works fine, I am able to press and the lights react accordingly.
If I attach an external monitor it still does not work, both screens remain black.
I have checked the monitor cables to make sure they were attached to the motherboard, and even unplugged the monitor and attempted to startup with only the external monitor, neither worked.
I am currently running 2.5g of ram, 512 located under the keyboard, and the 2g is newer (I know it is working) and located on the bottom.
I tried with both a fully charged batery and a low battery, both plugged in and not plugged into the ac adapter, and I also tried removing the battery and running straight off the ac adapter.
I also tried with the keyboard bezel completely off and made sure the close pin was not being pressed

Any suggestions with what could be wrong and how I could go about fixing this, or is this a lost cause?