Most SD card "write prevent" tabs are suggestions only. From Wikipedia: The presence of a notch, and the presence and position of a tab, have no effec

Most SD card "write prevent" tabs are suggestions only. From Wikipedia: The presence of a notch, and the presence and position of a tab, have no effect on the SD card's operation. A host device that supports write protection should refuse to write to an SD card that is designated read-only in this way. Some host devices do not support write protection, which is an optional feature of the SD specification. Drivers and devices that do obey a read-only indication may give the user a way to override it. In most cases the switch is just software detectable. Some prosumer cameras use this switch to indicate there is a firmware update on the card and that the camera should try to apply it when it is powered up.