Macbook: changed system password

[bigbadboss101]

Ok I picked up a used Macbook and changed the user name and password promptly. Now I am unable to get on the computer using the exact username/password. To break in do I need to phone Apple, or boot off an OS disk?

[Cos]

so you changed the password and now it wont let you log on?

[scary_perry]

If you don't have any important stuff on it yet, just reinstall.

[bigbadboss101]

I am reinstalling the OS. Nope, just picked it up hours ago and changed the pw but somehow it wouldn't let me on.