Dell E152 Flat Panel screen is REALLY dim.

I haven't seen this particular monitor. It may have deeply recessed black screws, or possibly even Torx screws. Try a #2 Phillips and see if it engages firmly. If not, try a T-10. Once you get inside, you will need to remove the power supply and main board to get at the LCD panel. Locate the inverter circuit - it will have two Teflon insulated wires going to (usually) the bottom corners of the panel. It may be part of the power supply board. Every LCD display I've seen so far uses pink colored insulation on those wires. It is possible that the inverter has failed, but most of the time, it's the fluorescent tubes inside the back of the panel.

Getting at the tubes without breaking something is not a trivial task. You will most likely need a #00 Phillips screw to remove the shield metal. Observe anti-static precautions from the moment you open the monitor. Be patient, and keep track of every part or connection you remove. Do not remove the LCD driver circuitry (generally at the top) from the panel. The tube(s) are usually at bottom, enclosed in a sheet metal reflector held in place by the bottom section of the thin metal frame around the panel, just inside a flexible white plastic sheet that covers most of the back of the panel.

You can get new backlight fluorescent tubes from www.lcdparts.com. This website has links to some very helpful pages on repairing LCDs. Note: replacing the tubes involves some rather delicate work. If you are nervous, twitchy or clumsy with fine work, you'd be better off to hire out the job. Be very careful not to rip the rubber insulators on the ends of the tubes when you slide them down the insulated wires to expose the connections to the tubes. You have to attach the wires at just the right spot or you won't be able to fit the insulators back on and get the new tubes to go into the LCD frame - and you can't apply heat to the wires for more than 4 seconds at a time. I've done a number of them successfully, but have occasionally had to try several times to make the connection sufficiently small and short.