Press the Windows key and R together then in the Run box, type Regedit and hit Enter.
Choose Backup from the File menu and take note of the location and name of the backup you're creating in case something goes wrong. That won't happen but it's good practice to do it anyway.
Next, navigate to HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Control/StorageDevicePolicies
Click on Write Protection and change the value "Data" from a 1 to a 0.
Exit the Registry from the File menu then restart the cmputer and try the SD card again.