Hi,
This will be a little long winded but here goes, as you know every Mac has a main user account which is called the root account and it is the system account that’s used to launch the essential background services required for your Mac to operate.
While this account is generally hidden and inaccessible, you can quickly get to it for its administrative capabilities by booting your Mac into single-user mode.
To do this you need to know the name of the account for which you would like to reset the password, and then perform the following steps.
1) Restart your Mac and hold down Command-S at the boot chimes.
2) When you see the command prompt, enter the following command to put the boot drive into read and write mode:
mount -uw /
3) Now run the following command to load Open Directory (Apple’s account directory service in OS X):
launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
4) Reset the password for your user account by entering the following command (replace “username” with the short name of the desired account)
passwd username
Just my thoughts