cannot reset admin password 10.4.11

Hi! I have a PowerPC G3 iBook, running OS X 10.4.11, which I bought a couple of years ago from a work colleague. It works great, but I want to change my broadband provider software, and need to input the Admin password to have the software installed. I have forgotten the Administrator password, so after trawling the internet I have tried to use the install disc that came with the iBook to reset the Admin password.

The install disc is version 10.2.1, and it lets me start (by pressing the C button on restart) and access the Change Password facility. I have changed the password, saved the changes and restarted the iBook. But when I then try to install the new broadband software, the new Admin password I've just set is not recognised! I have seen posts on the internet giving instructions on how to 'hack' after restarting and pressing the Command and S button, but I'm not confident in doing this because I've also seen posts on forums where people with 10.4.11 have had LOADS of issues after doing so! Please help? Do I need to try and get a new install disc nearer to 10.4.11, or is there another solution?? I don't want to damage a perfectly good iBook!! Thanks