These laptops have an inherent problem with the graphics card, to put it simply the solder melts slightly an the graphics chip moves and stops working. There are a number of ways to what they call reflow the chip, google "HP reflow"
. I have done it many times with the heatgun method, but once it starts it will always come back. You can also remove the battery, then tape all air vents up, wrap up in blanket and bubble wrap or the like, and switch on for an hour or so to overheat the board which reflows the chip, switch off, put battery back in, and switch back on again after it has cooled for half hour or so.
Note that reflowing the board is very hit and miss and can permanantly damage the motherboard, so only do this as a last resort when you have nothing to lose.
To be honest if this is the problem, then you need to get another laptop. This is very common with HP DV laptops,
The best way to check is to connect your laptop to an external monitor with a VGA cable. If it works OK on the external monitor, then it is a laptop LCD problem like a cable, or the screen itself etc. If it is still the same as described, then the above is almost certainly the cause.
Edited by jodav, 15 July 2011 - 02:58 AM.