I am posting this as information purpose and only once. Many will encounter once a while on multi card read where the computer OS prompt that it is write protected even if it is not. Sometime you managed to format it on the computer but the camera cannot read and asked to be reformatted.

Example: On WinXP, when you read the E:\ drive (SD card inserted), the OS prompted "The Disk is write-protected. Remove the write-protection or use another disk" message when you try to delete or write file.

Cause: the card reader side inner spring catch that is suppose to keep the lock in place is pushing it out of place causing the write contact to disconnect.

Temporary solution: use a thick tape or multilayer scotch tape and stick over the plastic lock to prevent the side spring of the card reader from pushing it.

Permanent solution: pry out the side spring so that the contact is loose. In the pic below, it is the inside metal catch that is causing the issue not the one outside.