on my 3DS how do you change write protected on the sdcard
Hello. Make sure that if the card have a switch it's positioned in the unlocked position. If it's already like that you can try to operate the switch many time and then retry. If it still don't work, put it in a computer. Mount the card, eject it (by clicking on it's drive letter) and retry again. If you can then write to it, try it again in the 3DS.
That didn't work. I'm not sure what you mean by "mount the card"
If you use window, the card should auto mount. It's a term that goes back to the unix era http://en.wikipedia.org/wiki/Mount_(Unix)Protected or not it should mount on the PC. You then need to unmount it (eject). That insure that nothing is wrote on the card while it's removed (as this can cause data corruption.You can also try with another card and tell me if you still have the same problem.