VIDEO FAILURE ?

This is what our technical experst suggest

The first thing to check in cases of complete video failure is the power status, as detailed above. If you can always hear your laptop fan when you turn on the laptop and now you can't it's not a video failure, it's a power or mainboard failure. The next troubleshooting step is to connect an external monitor with a standard VGA connector, whether a CRT or an LCD. If your notebook won't light up the external monitor, it's extremely likely that either the motherboard or the internal video adapter (if it's not part of the mainboard) has failed. If the video adapter is a discrete component and you can find a replacement for under $100, it might be worth gambling on replacing, but it's almost never cost effective to replace a mainboard. There is a small chance that the internal connection to the external video port has coincidentally failed with the laptop's own video subsystem, but it's not all that likely.

If the external monitor works fine, your failure is with the laptops video subsystem, which is usually contained entirely in the screen/lid assembly. There is a decent chance that one of the cable bundles (video signal or power) that run through the hinges to the video subsystem has failed, so unless the failure is obvious (cracked screen, fading in a corner, faint image, bad pixels), you should still open up the main body of the laptop as well to visually inspect the connections. The easiest problem to identify is obviously a cracked LCD, but a slowly increasing number of dead spots or whole rows or columns on the screen indicates the the actual LCD assembly is bad. Replacing the LCD is pretty much the same on most notebooks, Dell has a nice backlight design, the real challenge is getting the lid open and removing it without breaking anything.