Resetting a Nintendo DS Lite will erase all of the data on the system and restore the unit to its original factory settings. Once the Nintendo DS Lite has been reset, you can change its system settings and enter new information. Information that is lost during the reset can not be retrieved, so make sure you want to delete all of your information permanently before resetting your DS Lite.
Use the Phillips size 0 screwdriver to loosen the screw on the DS Lite's battery compartment. The compartment is on the back of the unit. Remove the cover.
Take out the DS Lite's battery pack. Carefully insert the end of the screwdriver or your fingernail into the tab at the top of the battery pack compartment and pop it out.
Leave the battery pack out of the unit for at least 10 seconds.
Replace the battery pack. Line it up within the battery compartment and push it back into place.
Put the battery compartment cover back on by sliding its tabs into the slots on the unit. Push the cover back into place and tighten the screw with the Phillips screwdriver.
Turn on the DS Lite. If the unit has reset, a screen will prompt you to adjust your system settings.
If you didn't get the "system settings" screen when you put the DS back on, you didn't keep the battery pack out long enough. Repeat the steps and leave the battery pack out for a longer period of time.