Changing passwords.

I recently acquired a mac from a friend. He has forgotten the password, I am unable to change the password without first typing in the old one (which I don't know) I have attempted to reinstall the OS, but to no avail. I am wondering if there is a way in which I may remove the old password.

You're going to have to do the old "wipe and install", erase the contents of the HD and re-install the OS. Follow the directions when you put in the install CD.

Is there anything of value on the hard drive that you'd want to salvage?

If you have the install media, then you can reset the pass word. Boot from the installation media, under the first menu item. Select reset the pass word.

oh and to boot from cd,
hold down the "C" key right after you turn your computer on.

Problem that I ran into was that I was able to reset the password, but when I restarted the computer, it would come to login screen, and I knew exactly what the password was, but apparently I didn't have the screen name. So since I had nothing of great importance on the harddrive, I decided to go to Utilities and do a fresh install. Thanks for all the help however.