All pictures in the internal memory and/or on the memory card can be erased at once. This is accomplished through either formatting or the "all-frame erase" function. I copied the following instructions from the advanced manual, which can be downloaded here: http://www.olympusamerica.com/files/d545zadvman.pdf
. Adobe reader should open that file with no problem. If it doesn't, that's another issue altogether.
1. Enter playback mode by pressing the play button.
2. Press the OK MENU button.
3. Press the right arrow button (next to the lightning bolt) to access [MODE MENU]
4. Then, press the down arrow to access the [MEMORY(CARD)] tab.
5. Select the [ALL ERASE] function.
6. Select Yes and press OK MENU.
(You'll need to use the arrow buttons to navigate the menus. Please see pg 16 of the manual for instructions on how to do so.)
Note: when the memory card is in the camera, it will erase the pictures off the card. When the card is removed, the function above will erase the internal memory.