Write protect problem with CF cards
 

I have several different San Disk CF cards which I have used but now wish to use them for something else. Trouble is that when I try to copy to them or erase from them I receive a warning that the card is write protected. Try as I may, even using a magnifying glass, I cannot locate a switch on these cards. Can anyone please assist? Thanks you.

What are you putting them in to read them?
 

Google suggests trying an external reader as internal ones don't mount them correctly giving the write protect error?

How are you accessing them? Camera, Printer, PC?

Very few CF cards had actual physical write protect, so as you can't find anything it's likely to be OS-related.

Have you a CF-USB card reader to plug into a PC?

SD

Don't Sandisk cards 'write protect' themselves when the flash fails?

I would try to check them in the last device they were used in. ie. camera. Many Cameras had settings to write protect your images for protection against accidental erasure etc.

You should, then be able switch this off in the camera and then reformat the card in the camera.