All you have to do is borrow some install disc from a friend. Boot while holding "option key" until a disc pops up on the selection screen (it will take a while to pop up) select it. this is called "boot from disc" at the top of the screen there will be an option to reset the password. I believe its under "utility" or something. You can try them all until you find the right one.
If you need another copy of the OEM discs, call apple. Tell them what you need, and they will send you a copy of the disc's for 18 bucks. It will be a copy of the original discs that came with the system.