You must stop recording mode first by tapping the (Rec/select) button at the TOP right of the unit. The word REC should disappear from the screen. Then follow these steps: 1. Press Menu (blue) button on the Front-left of the unit to access main menu. 2. Use Up/down buttons on the Front-right of the unit to scroll through menu options and highlight FORMAT SD CARD option. 3. Press (Rec/select) button on the Top-right to FORMAT card. Use Up/down buttons on the Front-right to highlight (YES) and press (Rec/select) to confirm. 4. When done formatting, the unit will return to video options menu. Press Menu button to EXIT settings. 5. Press (Rec/select) button on the Top-right to resume recording mode.