If you want to format a partition it should not be mounted
Plug in the card, wait for any messages and then do this command as root in a shell
umount /dev/sdc1
After this, you should be able to format that partition, for instance as ext3
mkfs -t ext3 /dev/sdc1
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…