I would say either your cpu or gpu is cooked, I've seen it plenty of times, the paste dries up/ fan not working/ heatsink clogged.
I had one laptop I took apart for a kid in my class a while back, they gpu/cpu was completely fried on it.
the only other time you wont get video is from bad memory. take both sticks out and look at them. place on stick in at a time and power on. swap them around and try again. if still nothing you might be out of luck unless you have memory lying around