If you connect up to an external monitor and can get an image by cycling through the Fn and F8 screen keys it's likely to be the backlight. Sometimes you can make out a very faint image.
Another possibility is the inverter but the symptoms are not typical (http://www.insidemylaptop.com/replace-screen-inverter-dell-latitude-d800-laptop/).
--- In simplycomputers2@yahoogroups.com, Ardell Faul <ardell@...> wrote:
>
> You are suffering from a co-incidence. There is nothing in the BIOS
> settings that you can do to make the screen stay off. Try plugging in
> an external monitor and booting it up that way. If you don't
> immediately see anything on the monitor, press the Fn key, down the
> lower left of the keyboard, and the F8 key at the same time. This will
> switch the video from the internal screen to the monitor. There are 3
> combinations, monitor alone, LCD panel alone, and both. Most likely
> your backlight has gone out.
>
> Ardell Faul
> Computer Monitor Service Inc.
> Ardell's Laptop and PC Repair
> 10816 E. Mission Ave.,
> Spokane Valley, Wa. 99206
> ardell@...
> 509-891-5188
>
>
> On 5/5/2011 3:27 PM, telegonus2 wrote:
> >
> > The screen on my laptop (Dell D800) went black last night and things
> > don't look good. It's fairly middle aged but not ancient, has been in
> > near perfect working condition but for wireless issues. I'd been in
> > the BIOS earlier in the evening and probably shouldn't have been
> > there. My reason was to get the wireless up and running, as I've been
> > using it with an external modem for a (now broken) pc. Technically,
> > I'm wirless, yet I've needed the modem for the signal for about four
> > months now. Otherwise, no complaints.
> >
> > I called Dell earlier today. The warranty has expired but they were
> > very helpful. By following their prompts and telling them what signals
> > I was getting they said the screen was the problem. My sense is that I
> > did something wrong with the BIOS (I'm a medium-sophisticated end-user
> > but no geek). One should always walk on eggshells when going there and
> > I maybe breezed through too quickly last night, about an hour before
> > it "went black" on me. My sense is that the problem is there, not with
> > the screen, and yet when I've googled the issue it seems that whenever
> > this happens on a Dell lap it's usually either the screen needs
> > replsacing, a bulb needs replacing or one has to buy an inverter.
> >
> > My sense is that while this may be so I still think it's something
> > internal, in the system itself, not a SOMETHING THAT NEEDS TO BE
> > REPLACED (but I'm admittedly an amateur at this). My chief reasons for
> > this are the relative closeness, time-wise, of the blackout to my
> > having been in the BIOS, my sense that I had done something wrong
> > there (disbled something maybe, by mistake). I know that screens
> > sometimes just break down but when I tried to hook up the lap to an
> > external monitor for my pc, and it was a perfect fit plug-wise,
> > checked all the wires, as they said, there was no picture. The
> > external pc monitor was as black as the lap screen,--yet the little
> > "night light" was on.
> >
> > Okay, that's it for now. I know that this is almost certainly going to
> > cost, and I'm cash poor right now (my fault,--LOL!--should've saved
> > for things like this). Any help or suggestions would be greatly,
> > hugely, majorly appreciated.
> >
> > Also: does anyone know if one can accidentally disable a screen in the
> > BIOS and get the black screen I have now? If this is the case, and the
> > Dell rep didn't think so, it would require taking apart the machine
> > and removing the coin-sized battery that keeps it going so as to shut
> > it down completely (no clock, etc.), which would cause the BIOS to
> > revert to its original state. Yet the rep said also that this is
> > tricky and she didn't want me to mess up/ruin my machine altogether,
> > yet I wonder if this is the answer. I'm tempted, not sure how to do
> > this without causing more damage.
> >
> > To anyone who has any suggestions/thoughts/ideas, in advance, I thank you.
> >
> > John
> >
> >
>
>
> [Non-text portions of this message have been removed]
>
