GTW-L17M103 LCD TV

SOURCE: BenQ LCD 17 inch Monitor

I wonder if this has a backlight in it. Most/or all LCD flatpanel displays use a backlight in them, namely a small florescent tube (a tiny version of the office florescent lights). If this is burn't out, or the little power supply which runs it dead, you will have a black display. The image is actually there, you just can't see it, except perhaps faintly when external light hits it just right. The display must be disassembled to check this light. If you have tech savvy, and some equipment, voltmeter, maybe an oscilloscope, you could check it out. Where to get a replacement lamp? Google it... perhaps the manufacturer.

SOURCE: lcd tv

To solution #2 
My TV has  the same problem. Where can I get the parts for backlight/lamp and capacitors?

SOURCE: Gateway 26" LCD Power Supply

There is a silver lining....
Unless you physically see burned components on the power supply main board, it
is not fried. If you examine the board on the back side ( solder joint side) you will notice that there is a devider that is clearly marked between the Primary and secondary sides of the board. There will also be a large transformer accross this area.
All switch mode power supplies have optical couplers which cosist of a light emmiting diode usually infared and a photo transistor. These are for protecting the secondary side of the board or the expensive side. A typical switchmode power supply for an LCD tv will have at least three of these. They are roughly 1/4 inch long and 2/8 inch wide
and are black with four leads. They will be directly accross the marked portion of the board that seperates the primary or high voltage side of the board from the secondary.
These opticle couplers or switches cost an average of $ 7.00 a piece and are available
from any electronics supplier such as NTE.

I hope this helps. Remember it can all be repaired. Its a matter of if its economically
worth your time.

SOURCE: ccfl inverter board

where can I buy a new transformer

SOURCE: Gateway FPD 1830 18.1 in. Flat Panel Problem

Usually in these cases the power supply would be the issue, but you say the OSD window shows up clearly, So the LCD panel is good and the Power Supply /inverter depending on which your FPD has.
FPD 1830 should have 3 boards(logic, Inverter, Power) otherwise just 2(logic, power)

If it is super dim, the problem is the inverter. Or the Power Supply if the inverter is embedded

Otherwise what your issue is the logic board, if you can swap out that part for a good one, Chances are for sure that you will have a spanking new FPD working.

I've worked with these a lot. Im working on one right now.
I hope this helps
Wish you luck
Victorsinferno45