A:Answer Mp4 is the format of the videos, not the micro sd card. You probably have to format the card on a computer first. Use a card reader and it should show up as a drive (like F:\SanDisk for example) when you plug it in. From there make sure it's empty since formatting erases everything. Right click and choose Properties, then the Tools tab, then Format. If the default settings don't work try again choosing FAT32 as the formatting type.