Damaged 2009 MacBook Pro

I am attempting to help a friend save a few dollars and learn a thing or two about MacBooks in the process.

So, she dropped her 2009 MacBook Pro and smashed the screen but no damage at all to the unibody. When you tried to turn it on you got a power light but the screen and keyboard were black. HDD spins for a while then clicks off. Fans running OK. Apple estimated $800 repair and all data would be lost. Data recovery guys wanted $2000-$3500 to recover it.

This is what I have managed so far:

Removed the harddrive, bought a $7.99 lead off the internet, and used my iMac to make a complete back-up of the harddrive so there are no problems with that. Reads fine, no weird sounds etc. I then replaced the glass screen and the LCD for about $70 so it now also looks good as new but...

When you turn it on you still only get the power idicator, good battery charge indicator, keyboard is unlit, caps lock has no effect, screen is black (as before so there was probably never a problem with the actual LCD but it's easier to replace since the glass was coming out anyway). Cannot boot in safe mode. Tried to boot from an old Snow Leopard DVD which spins but still the computer does nothing... and now I can't get the disk out!

Tried swapping my good HDD from my other MacBook Pro into the damaged one and it still doesn't boot. Ram is seated correctly. Nothing looks out of place, cracked, loose, disconnected etc.

So, what part of the start-up process makes the system look at the HDD and boot from it? Are there any other combinations of buttons I can push to try a force the thing to talk to itself?

Thanks.