Searching for an Inverter for an Inspiron 1100 will be all you need to search on eBay. There are several people who sell new ones for about $15 to $18.
I agree that it is the likely cause.
The tricky part is when it arrives. You need a #1 philips screw driver of high quality steel. You will have to remove 7 to 9 screw covers which are rubberized. They just pull or pry out. Then remove all of the hardware, and the screen. All together, there are 18 very small screws. If your memory is bad, photograph each step along the way. The inverter will be on the bottom of the screen beneath the screen. It has two sockets which must be unplugged. Replace the old one with the new one. Reassemble using the blue screw goop that keeps the screws from falling out. WalMart and hardware stores have it. Coat the threads with blue, then screw them in. Use a medium grade of rubber cement to replace the screw covers. In an hour, you are done.
If that doesn't work, you need a new screen which installs the same way... and costs about $100 to $140 for a new one, plus shipping. There are several suppliers on eBay, and several *****s. The best one uses a screen that permits adjustments to the output. The best new ones allow adjustable light output, and come with the inverter.