how old is it? older DV laptops have a huge problem with the gpu's, even to the point of a class action. Sounds like a GPU problem though.
Basically, the solder between either the gpu and the motherboard, or the solder between the chip layers itself starts to break and create fractures. once these fractures create a full break and don't stay connected anymore, the gpu doesn't work.
you can either get someone to reflow the gpu to try to mend those solder breaks, or replace the gpu via a reflow machine, but both aren't a cheap option and usually with an older laptop, i tell people to replace the laptop. not worth spending $100 plus on a maybe temporary fix.