My dv9700t stopped displaying video today. I opened it up this morning, the Vista login flickered a few times, and the PC rebooted. After that, nothing has shown up on the screen (or external monitor) even though it appears to boot. The backlight comes on and stays on when the lid is opened, so I doubt it's a backlight or inverter problem. I was thinking it could be the lid switch but the backlight turns on and off when the lid is opened and closed. I tried power cycling the PC (taking out the battery and unplugging it) and even took out the CMOS battery but none of these fixed it.
The problem seems an awful lot like:
HP Pavilion dv2000/dv6000/dv9000 and Compaq Presario v3000/v6000 Series Notebook PCs*-* HP Limited Warranty Service Enhancement*
"The following symptoms apply to the dv6000, dv9000 and v6000 series notebooks:
* The notebook does not detect wireless networks and the wireless adapter is not detected in the Device Manager.
* There is no video on the computer LCD panel or external monitor.
* The notebook has no power and no active LEDs.
* The notebook does not start.
* The battery charge indicator light does not turn on when the battery is installed and the AC adapter is connected.
* The notebook issues a single beep during boot indicating no power.
* The external monitor functions but there is no image on the notebook LCD panel."
but says that the dv97xx series aren't affected by whatever defect happened to those other dv9xxx models. I question that, as the dv9700's video card runs hot (the page says a new BIOS increases fan speeds) and if that's the source of the problem definitely needs to be included.