The photos are write-protected because they have been protected against accidental deletion in the camera. To cancel the write protection, go to Playback in the camera menu, select "Protect" and then the option to cancel the protection for individual or all images in the folder. To do this, press the centre of the setting wheel for the protected images until the tick disappears and confirm with OK.

If the write protection comes from the SD card itself, check the lock switch on the card. If it is in the locked position, you cannot write any data. Move the switch to the unlocked position to remove the card's write protection.

It can also help to check the write authorisations on the computer and adjust them if necessary if the card appears there as write-protected.