Please note the fact that it only works if the password to the MMC Card was set in ur own mobile,where u want it to be unlocked. This method works well for nokia cells with symbian operating system.Never tried on other cells.use any software like FXplorer that can browse files in ur cell.
1. Open one of above software you have.
2. Browse through the directory, C:\system
3. Rename the file mmcstore to mmcstore.txt
4. Open the file - The file will open in Notes.
5. You will find your password in that file. That file would also contain much more data which you do not understand,so you need to go through the file to get the password!
When ur cell is connected to pc by means of data cable or bluetooth,u can see the password by simply opening the file mmcstore with notepad.