It sounds like the backlight is dead. It's a shame because the bulb inside is worth maybe 1$.
If you want a chance to save some serious money, look for display refurbishment, resale, recycling and repair sites. Call them up and tell them you need a backlight replaced and see what they say.
First, back up absolutely everything on your HDD. Mirror it if you can onto an external drive.
If you're feeling brave, break out a set of jeweler's screwdrivers and start disassembling your notebook's display lid. Screws are usually hid under rubber stops, stickers and other things. There will be internal latches holding the notebook lid together made of plastic that also need to be teased apart. Once you get inside, there will be a LCD module connected by either a ribbon cable or bundle running through the hinge which carries the data to the screen. The backlight bulb is usually along the bottom edge of the display and is connected by a much simpler 2-wire cable carrying the relatively high voltage necessary to make plasma in a flourescent bulb.
The backlight's drive circuitry may be either in the notebook lid by the LCD or, in the notebook base. The circuitry transforms the low voltage DC coming from the battery through the motherboard to a high voltage AC. If the circuit's output is hot when the backlight is supposed to be on, it's good and the only thing that can be wrong is the $1 bulb itself.
If you determine the bulb needs replacing, the display is far more delicate than the floppy plastic lid that contains it. You may consider buying a whole new (used) LCD just to get one with a good bulb. Otherwise, replacing just the bulb itself will require a very cool head and steady hand. Don't take apart anything you don't have to when dealing with the LCD. Even microscopic lint, once inside, will be there visible forever.
Don't do anything without having a replacement bulb ready and waiting to swap with the old one. And, good luck scavenging a bulb of exactly the right length.
I have a two year old Sony Vaio VGN-a190 laptop with the 17 inch xbrite lcd screen. Yesterday the screen would not come on. I can seen the faintest hint of the screens and the computer functions normally. After doing the normal troubleshooting I paid Sony $20 bucks to troubleshoot. After about 10 minutes they told me that it sounds like the backlight went bad. I can send it in and have it repaired for $768 plus shipping. Do you think it's worth it? Any other ideas b/c I'm not 100% convinced it's the backlight.