Notebook PC Model 1664 BLACK SCREEN AND POWER BUTTON ONLY FIX
I tried booting up my faithfull HP g series notebook computer the other day and I got a black screen and a power button and fan noise and nothing else. So I turned it off, put in the emergency Windows 7 boot disk, same thing happens as the computer is NOT posting (no BIOS info shows on screen, toally black, no hard drive activity). By now I am alarmed. But I sit and think "If, like most electronic devices, there is a static charge build up of some kind, the device does not work"
SOLUTION: unplug power supply, remove battery for one minute. Put battery back in, and it started up like a charm!
Note: if this does not work for you, and there is no hard drive activity, it may be the power supply.