Mike has an HP Pavilion G Series laptop and the screen has gone black. Is the screen dead? Leo says that it could be. In laptops, it's often a frayed ribbon connector that has obstructed the video signal. Mike should try hooking it up to an external monitor to see if he can see it. If he can, then he'll know the computer is OK but the screen has either died or the ribbon cable has broken. But if he can't see anything with the external monitor, then it's probably the video card that has died or the motherboard has failed. And due to the age of the computer, there's really no user serviceable parts. So it's not worth repairing.
From the chatroom, it could be that the soldering on the motherboard needs to heat up to reconnect. He could wrap it in a blanket and let it heat up to see if the solder reheats, but Leo doubts it. He thinks the video card, which is on the motherboard itself, has died. Replacing the motherboard in a laptop is almost as expensive as replacing the entire laptop. So he may as well replace the whole thing. He should take out the hard drive and get a USB external housing to plug it in and get his data off it. Newertek makes a universal hard drive adapter for that very purpose.