Mac startup disk

With a Mac startup disk, you can do several things.  If you hold down the Option key or the C key while booting up and immediately insert the Startup Disk, your computer will boot to the Startup Disk.  From there you can choose Options.  If you haven't already set a Firmware Password, anyone with a Startup Disk can change your passwords and access your computer.  You might think you are safe without a Firmware Password but you are not.

I bought my laptop from someone on craigslist.com.  He only has a Startup Disk for Version 10.4 and it didn't give me access to change or set my Firmware Password.  I'll see if I need the Startup Disk for Version 10.6 in order to do that or if I missed something.