You hear it all the time: For better images and more control, shoot RAW. Why? Because when you shoot JPEGs, all your decisions about brightness, contrast, white balance, and more are written into the file forever.
But with RAW you can adjust those things later with conversion software. If you have Photoshop CS or later, try Adobe's Camera RAW to do the processing. To get into the program, double-click a RAW image in Adobe Bridge, or, from Photoshop, go to File > Open, and choose a RAW file.