No Admin Password Or Cd

i have a macbook that i got used, when i got it had an admin password set and an open account, i have no way to contact the previous owner, but there didnt seem to be any restrictions set, so i figured i could live with it.

but then i tried to download GIMP, and it said it needs an admin password, that's bad because i need GIMP for my work.

is there any way to reset the admin account without destroying my computer, losing any files, or having the original CD?

If the account you are on is an administrator, you can simply delete the old account.

My dad is new to computers and forgot his password. He couldnt install updates and the likes and absolutely could not remember his password. I found a how-to on booting into single user mode that will allow you to reset the password. It requires a significant amount of typing in a terminal type environment where one little misspell or missed space etc will cause it not to work. If you are comfortable below is the link to it.

It worked great for me. In my case it didnt work the 1st couple of times because I finally figured out that my dad's username started with a capitol letter and this process is case sensitive so keep that in mind.

Also be advised this rids your Keychain of all it's passwords. That may be a pain for some, but in this case was much better than an OS reinstall.

Also this is for Leopard. I am new enough to Mac that I can't say what versions this works on, but am sure you can find a similar how to for your OS if this is irrelevant for you OS.

LINK to Article.