Ok, for once I have a question rather than a possible answer...
My client's laptop is an old HP Pavilion ze4600. When he brought it in, the LCD light was on, but the screen was black. I assumed it had crapped out trying to resume from hibernation. I hard-powered down and brought it back up. Voila...came right up no problem. I added memory (he only had 256MB installed and with shared video...yeah...not speedy), cleaned up the drive, reinstalled Norton 360 (don't get me started...told him we'd be changing that as soon as the license expired), and got it running better than the day he bought it.
Here's the problem...that was last week. Today, he calls me with the same (seeming) problem. When he got here, I tried the same solution to get it running. No luck. The backlight comes on as per usual, but I don't even get the HP bios screen! This tells me it's NOT a driver problem. I let it run as per a normal boot cycle and the HDD eventually calmed down and the screen even did a blink-out for a second as it does during normal booting. Once the drive stopped accessing, I did a Win-key shortcut to shut down, waited a few seconds while the HDD went nuts, and it shut down like normal. This tells me that Windows is running just fine!
To make matters more interesting, I tried hooking up an external monitor. The monitor is known working. Crap picture, but it works. Unfortunately, it wasn't getting anything from the laptop. Tried a cold boot and everything. No picture. At this point, I'm getting a bit worried...there's apparently no video signal AT ALL.
During the most recent bootup, I started hitting "Fn + F5" (the display selection hotkey) repeatedly. Now, I realize that this is a lot like hitting "ESC" during a command-prompt function instead of Ctrl-C and really doesn't DO anything...and yet, suddenly, there's the Windows loading screen on the laptop!!! Still nothing on the external monitor, but the laptop screen is working again.
I checked the Windows logs and found no errors of any kind. Seems I did my work well last week. Unfortunately, despite cycling through the display settings (Fn + F5) from within Windows, I still couldn't get anything on the external. This includes "external only" mode where the laptop LCD is turned off. Nothing.
So, here's the actual question: is it possible, or perhaps likely, that the video processor itself is malfunctioning? I mean, no external display, and intermittent loss of the LCD picture seems to indicate this, but I have little way of determining for sure. Any suggestions on another cause or possible solution other than having the laptop replaced?