This may be a hardware problem, but I'm not sure...
I have Vista Home Premium SP2, 32bit. My HP laptop has an NVidia graphics card. I usually it it in my office with an external 19" display -- usually only the 19", but lately I've been using both the 19" and the laptop display for more real estate.
Today while I was working the laptop display suddenly went black, like a screen saver had just gone on. (I don't have any screen savers active.) I opened the NVidia control panel and set it back to "just laptop display" and the laptop display lit up just fine. Huh. OK, then I set it back to both screens and everything was fine.
Then about 3-4 hours later it did it again -- but this time I can't get it to display on the laptop. I tried with the Nvidia control panel, and I tried unplugging the dock that the 19" display is attached to. If I unplug the external display, I'm left with a dead screen on my laptop.
Except -- it's not TOTALLY dead. When I set it to laptop-only, or when I unplug the external monitor, the laptop display flashes on for a second and then goes out again.
Huh. And now I just tried setting it to the laptop again, and it worked. I've got it on both monitors again... for now.
Does this sound like anything software-related, or is my laptop hardware getting flaky? The fact that it flickered on for a second when I turned it on, via software, through the NVidia panel, make me think it might not be hardware...
It's hard to say for sure, but this does sound like a hardware failure. How old is the laptop. I do not know all the ins and outs of how laptops screens work, but this could be some kind of backlight issue with the screen. A visit to a computer tech may be in order.
Confirm that power settings on your laptop are set to "always on" with no monitor or other time outs.
Ensure that laptop is always pluged into power source (outlet).
Ensure both monitors are set to "always on".
Clint, this was happening while I was actively using the system. When it didn't work, it didn't work even when I actively directed the system output to the laptop monitor. I'm quite sure it wasn't a screen-saver type of thing.
Ted, the laptop is 2+ yrs old. Still appears to be in very good shape. But you never know...
I have heard of similar problems with laptops that are not "old". Unfortunately you may have the 1 in a thousand that dies early. A tech specialist (repair person you trust) should be able to T/S the problem for you. Unfortunately I do not have the tech expertise with laptops to recommend any self T/S steps. Perhaps someone else with this expertise could step in here.