I have a friend whose laptop screen has stopped working after he hooked it up to his TV. He still sees the XP boot screen, but it goes completely black when entering Windows. How can he fix this? It's an HP laptop but I'm not sure the model number.

Answer:
It's probably still pumping the video out the VGA socket. Is there an F-key with a picture of a screen on it? If so try pressing Fn plus that key. Otherwise plug the TV back inand, if that gets you a picture, try switching back to the laptop screen through Properties on the desktop.
Answer:
Try clicking the button that looks something like this l0l with hp there are often three combinations, so click it once and wait, if nothing, click it again, it should come back.
Answer:
try going in safe mode by pressing F8 key and there i think you can set your screen as primary screen in display settings
Answer:
doesnt matter the model number, check the cords to make sure they are in the right positions.
Answer:
Is it still hooked up to the TV? Try pressing Fn + f4