You can change the root level password by following the steps given below:
You need to boot the computer system with Linux Mint 10 Installation CD.
After the system starts to boot you may need to enter into the Linux mint 10 Rescue mode by typing boot: Linux Mint 10 rescue in the boot screen.
When the sh prompt is reached you may enter the following given command to change the root level password
chroot /mnt/sysimage
passwd
Where “passwd” is the new password and the password will be rested to the new one.