No external display is attached-i dont know what to do

Does your display work when you enter the BIOS? Have you ensured your display settings brightness are turned up?
Attach an external monitor - Look for the projector display on your keyboard (it could be F5, F6, F7, F8 - depending on your model). Often attaching external monitor will auto display monitor selector. Select "duplicate" - if your monitor still doesn't work on your machine but does on the external monitor you may have a hardware issue.

You can't just attach an external monitor to most running laptops. Nothing will happen. You must attach the monitor when the laptop is off, then start the laptop and it will recognize the external monitor and send the video to it.

I have the same problem, It works at an external display and the lcd and lcd cable work on another laptop.
The problem is that i have a sony vaio and it has no inverter, or at least i dont see one like an hp laptop for example. i tried to switch image from external monitor to lcd and it doesnt work. i tried everything. dont know what to do more, Hope you can help.
I have a Sony Vaio pcg-61813M.
Thanks.

Guess what? I don't see it either.

Oh,....that's because you're there, and I'm here, and.............never mind.

(OH, I'm jus jokin'!)

Would be helpful to know the laptop manufacturer name, and model number, though. The name you know, the model number is on the bottom of the laptop.

Diagnose to see what the problem is;

A) Graphics chipset,
Or
B) Video Cable,
Or
C) In the Display Assembly

1) Suggest start with attaching a VGA monitor to the laptop.

Laptop OFF, monitor OFF, attach the VGA cable of a VGA monitor, to the VGA connector on the laptop.

Example of a VGA Cable, and VGA connector,

http://en.wikipedia.org/wiki/VGA_connector

You can use a CRT type of monitor, (Looks like a small TV), or a flat LCD screen monitor if it has a VGA cable.

2) Turn the monitor on. If a CRT type allow it to warm up.
Turn the laptop on. By factory default the display should show on the external VGA monitor.

IF not;
There are at least 3 display options available,

A) Internal monitor of laptop ONLY
B) Internal monitor of laptop AND external VGA monitor
C) External VGA monitor ONLY

Hold the Fn key down, and tap once on the Display Toggle-Over key.
Which key is the Display Toggle-Over key?
Don't know. You didn't state the laptop manufacturer name, and model number.

It is one of the F keys at the top. F1 through F12.
Usually has a monitor symbol on it, and a side arrow.
(Most of the time the F4, F5, F7, or F8 key)

No display on the external VGA monitor?
Hold the Fn key down again, and tap once more on the Display Toggle-Over key.

Still no? Bad graphics chipset.

Display shows on external VGA monitor? Problem is the Video Cable, or in the Display Assembly.
Post back in a Comment after you have performed this procedure, and also post the manufacturer name, and model number.

If the graphics chipset is good, we'll go on with the diagnoses if you wish.

Regards,
joecoolvette

Seems that you have a loose LCD screen cable connection. You will need to disassemble the laptop & make sure the LCD screen cable connection is tight.
Please check this link for more details:
http://www.laptopparts101.com/lcd-screen-video-cable/

goto your control planel select display settings on the notebook to adjust the selected monitor. Than test monitor 1 or 2. What OS are you using it is alittle diffence. XP or vista; vista has personalization and xp go into display properties.

Using the Display When you start the computer with an external device (such as an external monitor or projector) attached and turned on, the image may appear on either the display or the external device.
Press <Fn><F8> to switch the video image to the integrated display only, the integrated display and an external CRT monitor simultaneously, an external CRT monitor only, the integrated display and an external DVI monitor simultaneously, external DVI monitor only, and external CRT monitor and external DVI monitor simultaneously.

Are you sure it's "F8" only? Usually most laptops use the FN+F5 to change video to external display.

Attach a external monitor to the laptop, it will have a VGA connection on the back or side. You will need to press, function and one of the F keys, F5 or F8 which are standard ones. So function and an F key. This will rotate the display from the laptop to the monitor and vice versa. If you get the display on the external monitor then you have an LCD or inverta(controls power to LCD screen) issue.

If there is no display to the internal or external, then you have a bad motherboard.

Sounds to me like you have a short inside your system somewhere, or you have a faulty display/graphics card is going bad. You will probably have to replace your display and/or graphics card. On most laptops, if they dont have a dedicated graphics card, and they use an embedded one, then the whole screen has to be replaced. if the graphics card Is dedicated, then you probably can just have the card replaced, and not the whole screen.