Do you have your laptop set on a power-saving mode? Check the power settings. My netbook has a battery manager function that enables me to adjust the LCD brightness level when I'm not plugged in so that battery life is optimized.
You also might want to check the brightness settings that are accessible (probably) through your keyboard to make sure you haven't turned down the brightness on the screen by accident (a possibility, as I know a FN + F5 will do that on mine).Edit after doing further research:
FN + up arrow on the keyboard will increase your screen brightness. If that doesn't work, right-click on the battery on your taskbar, click on Power options, choose whatever power plan you are set on, change the brightness levels, choose to save, and that should work.
Since this system is running XP, I'm presuming this is not a new system. If it were and you have always had this problem and never been able to resolve the brightness issues, you need to contact Dell Technical Support. Your system is under warranty and there could be a problem with your display.
Edited by txtchr, 12 April 2009 - 03:31 PM.