First try to recalibrate the screen (start up the DS, and do the following--text from nintendo.com):
- Remove all games from the Nintendo DS.
- Turn the system on by pressing the POWER button.
- Press the A Button when the "Touch the Touch Screen to continue" message appears.
- When the main menu appears, use the Control Pad to to place the cursor over the Settings Menu Panel at the bottom of the screen, and press the A Button.
- Use the Control Pad to place the cursor over the orange icon that looks like crosshairs (the right-most icon), and press the A Button.
- Use the stylus, and tap the red square that appears on the screen. Do this each time the square moves.
- You must touch the red square precisely at each of the three positions, otherwise the test will continue to re-start.
- Ifthe touch screen is not responding properly, hold the Nintendo DS at anangle so that you can see where the edges of the Touch Screen meet thehousing of the system. Look around the entire edge of the Touch Screenfor any foreign material (such as crumbs, etc.) that may be wedged inbetween the Touch Screen and the housing of the DS. Foreign material inthis area can cause the Touch Screen to work incorrectly.
If the screen still does not work, you need to buy a new touchscreen. Many vendors sell these, here's an example:
You will need a good tri-wing screwdriver to do this repair (don't buy a cheap knockoff--they will strip your screws). Try one like this: http://www.play-asia.com/paOS-13-71-1e-49-en-15-tri_wing-70-1fe.html
Then follow the step by step tutorial at: