I have been given a DS Lite. How can I rename it
http://www.nintendo.com/consumer/systems/ds/settings.jspSee changing your nickname.
there should be an icon on the lower screen at the bottom center, click it to go into settings to change all settings including the name,date,color scheme, birthday and other settings.
Start calling it by the new name. Adoptees tend to start responding to their new name pretty soon.
If you mean the DS has an internal name, boot it up without a game inserted, then go thru the menus to reset to factory settings.