Well the oher way is to find a startup dvd and change password via utilities.
i am trying to enter safe mode to reset password but on start up command + s wont work.
safe mode is the shift key & doesn't get you in single user mode.
single user mode:
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.
http://support.apple.com/kb/HT1492
It's lower case s. Did this today & worked. Hold down until typing comes on screen.
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.
I just bought brand new mac keyboard since my was lost.
Is it wired? Must be wired. Try some pc keyboard. Use the windows key for the command key.