Using Curves to Adjust Dark Photos
Using Adobe Photoshop 5.5

Before

After
1) Open Image
Go to File and Open. Find your image and select open.
   
2) Image, Mode, RGB
Go to image, go down to mode, and then down to RGB Color
   
3) Make Background a Layer
Double click on the Background layer and rename it to Layer 0. If the layers palette is not showing go to Windows , Show Layers.
   
4) Image, Adjust, Curves
To use curves to adjust the dark photo go to
A) Image
B) Adjust
C) Curves
   
5) Select the Point
For this picture select the point showed. This will lighten or darken not black but the darker colors.
   
6) Adjust
A) If your photo is too dark click on point A and move the arrow up

B) If your photo is too light click on point B and move the arrow down