Thanks for that information, very interesting ... However ... ;)

On three occasions I've needed to boot straight into single user mode, or boot from the install CD, to recover my system after I've messed it up. This tip would stop me doing it. Can anyway comment on whether this is a good thing to do if you are regularly experimenting with the system? Although I don't really treat this machine as a production machine, I still want to limit it's use to anyone who might get their hands on it.

Note: I'm not saying this is a bad thing to do, but if like me, you like messing with config files and installing new versions of software, it might cause problems recovering from any serious errors ...

Hold down the option key when booting. It will ask you for your password(Open Firmware). You will then be able to select another disk(cd). You can also use the same app to turn off the security, it isn't permanent.