Instructions
Push the power switch to turn the console on. The console will boot into the DSi menu.
Tap the camera icon to enter camera mode.
Tap "Other" on the camera menu. A screen with several icons will appear.
Tap "Delete" on this screen. A prompt will appear, asking you which location to delete the photos from.
Tap "Delete from System Memory" if the photos are stored on the DSi's internal memory or select "Delete from SD Card" if the photos are stored on the removable memory card.
Tap "Photos."
Tap "All photos" to delete all photos stored on the chosen storage location. Tap "Delete individually" to select specific photos to delete. Additionally, you can delete all star-, clover- or heart-tagged photos by selecting the appropriate option in the menu.