such a problem can easily be resolved on Nokia phones. If a SD card is blocked due to the fact that you have lost or forgotten its password, you can easily trace back the password.
First, you should get to its File Manager or the Application Manager. Under the Settings feature, you will have to look for the MMCSTORE file. It will normally be found in the System folder.
Look for it and send it to your computer by using your PC Suite. You can get it transferred via bluetooth or a USB cable.
As soon as you have it on your PC, right click and select Open with. Select opening it with the Notepad application.
This is where you will obtain the specific password that you are requiring