The exact message would be helpful. I doubt this is it:
uknown puplic ato
Let's establish exact machine specs.
Here is how to find out what version of Mac OS you are running:
Click on the blue apple in the upper left hand of the screen.
click on this icon
Click on the first line, "About This Mac"
Most of these are numbers & that's what we want.
What version & Processor do you have?
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Get the Mac to set up an additional administrative account. You can then change the password on your old account.
Start with your computer power off. Hold down command-s. Power on your computer.
Type in the following:
The first two commands will depend on your release of Mac OS X. Look at what is typed out in the console to determine the exact format.
# Type the follow two instructions to access the startup disk in read/write. Press return after each command.
# in case of partial success repeat this command until errors go away.
/sbin/fsck -fy
/sbin/mount -uw /
cd /var/db
pwd
#List all files. The l is a lower case L.
ls -a
#The move command acts as a rename command in this format.
mv -i .applesetupdone .applesetupdone.old
# reboot your mac
shutdown -r now
Once you've done that the computer reboots and it's like the first time you used the machine. Your old accounts are all safe. From there you just change all other account passwords in the account preferences!!
Limnos adds detailed explainations:
http://discussions.apple.com/message.jspa?messageID=8441597#8441597
The above the idea came from a post by JoseAranda at September 9, 2006 3:48 AM
http://www.askdavetaylor.com/how_do_i_reset_my_mac_os_x_admin_root_password.html
You will need to scroll down to see this post. Search for applesetupdone
This method is mentioned in an apple support page without giving an explanation.
Once you have a new administrative account, you can change the password of your old administrative account
blue apple > System Preferences > Accounts
