No password for iMac G3.

I bought a used iMac G3 off of craigslist just to play around with the Mac OS a bit. The person I bought it off of has a password in place but failed to inform me as to what it is. Is there any type of password recovery program for the Mac that I can use? I do not have any system discs and I am not really all that sure which version of the OS I would need should I decide to go ahead and just buy the OS to do a re-install. I know that it is running a version of OS 9. Any help would be great.

 

I guess I did not even realize that there was a forum dedicated to Macs on here. Thanks!