I've got a HP Presario C700 laptop/notebook here. I've been playing with it for hours trying to get it to work.
From boot all there is, is a white screen with some coloured lines on it, you don't see anything at all but it will still boot and load windows as normal as you can hear it but yeah there's no screen.
So I've plugged in an external monitor with a VGA lead and on that, if I set the laptop to just use the external monitor everything works fine, you see it all from boot but if it has anything to do with the laptop itll give the laptop a white screen and the external monitor will have a working screen but itl go down to like 568x600 screen res and everything is wavy and moves slightly.
I've tried it connected to the other screen and booting in to the BIOS and it all says its fine but I can only get into the bios with the sh*t res.
from the event viewer and various pop up's I think it's the graphics driver failing but I cant find and/or it wont install an updated version of the driver
Sounds like the screen is broken or something is not connected correctly, have a check to see if anything is unplugged. If you type the model of you laptop in to youtube you should be able to find a guide how to open it up. (like this one How to replace lcd screen of HP Compaq Notebook - YouTube)
I've had this both ways around - laptop working and not external, external working and not laptop, and in all 4 cases it was the video bits on the motherboard and only a replacement motherboard would work.
Unless it has hdmi then you could use that with a VGA convertor - that might work?