How can i reset my administrator password

Question

my brother passd away not too long ago and we havent been able to update anything cause we always asked for a password any help??? i do not have to disk to reboot :/

Answer 1

Forgot Your Account Password
For Snow Leopard and earlier
     Mac OS X 10.6- If you forget your administrator password
For Lion/Mountain Lion
    Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
     When the menubar appears select Terminal from the Utilities menu.
     Enter resetpassword at the prompt and press RETURN. Follow
     instructions in the dialog window that will appear.
     Or see Reset a Mac OS X 10.7 Lion Password and
     OS X Lion- Apple ID can be used to reset your user account password.
If you cannot do the above then try this:
  1. Boot to Safe Mode by restarting and after the chime press and hold down the COMMAND-S keys until a black screen with white type appears.
  2. At the prompt, type the following commands pressing return after each command line:
     /sbin/fsck -yf
     If you do not receive a "Filesystem OK" message then repeat this command until
     you do.  If after seven tries you still do not receive a "Filesystem OK" message,
     then the system is corrupted and needs to be reinstalled.
     mount -uw /
     cd /private/var/db/netinfo
     mv local.nidb local.old
     rm ../.AppleSetupDone
     shutdown -r now
The second-to-last command above will cause OS X to think that the operating system is newly installed, and when the new owner starts up the computer it will send him/her to the startup wizard where he/she can start a new user without reinstalling.
This last method does not actually change a password. It simply removes the user accounts and lets you create an initial admin account as if the computer were new out of the box.