I suggest you write down all you passwords on a piece of paper or save in a file which you backup.
Changing password from single user mode:
You can also change the administrator's password from single user mode or create a new administrator account.
You need to get into single use mode for steps one and two that are listed below.
This page will tell you how to get into single user mode.
Basically, you hold down the command-s key then powering on your machine. The command key has a little apple symbol on the lower left. It is between the alt/option key and the space bar. On a PC keyboard, it will be the windows key, I think. The boot up will take longer than normal. The filesystem will be checked and repaired.
1) You can change the password on an account. ( Do you know Unix. You are in a Unix single user console. ) The setup commands you need should be listed on the screen. For Mac OS 10.4.11, the commands are:
# Type the follow two instructions to access the startup disk in read/write:
# ( in case of partial success repeat this command until errors go away. )
/sbin/mount -uw /
->Start up some utility processes that are needed.
->You will probably need to press the return key once the system stops typing.
->To find out the users on the system type, use the <b>l</b>i<b>s</b>t command. The l is a lower case L:
->One of these accounts will be the administrator.
->Pick one of the users which I'll call a-user-name and type it in this command:
->and enter the new user password. You need six characters.
->You will need to enter your password twice. Your typing will not show up on the screen just
-> press enter when you complete the typing.
->For cryptic information on these commands try: