Black screen laptop - Works with external...

Hi,

I have an issue which is perplexing me. I have been given a friends laptop to look at.
The screen is black when switched on, but you can see all the LED's and, hear Windows start up. I hooked it up to an external screen and it works fine in every way. I ran a few checks graphics driver and all is well.

I've tried taking everything out and put back in again (dvd, ram, HD). I've changed the screen and inverter. And it's still hasnt made any difference.

It's an HP Pavillion dv6000

Hope someone can shed some light on this.

Thanks
Ben