I am writing this on my Mid 2007 Mac mini running Mac OS X 10.6.8 Snow Leopard because I really messed things up last week. Thank goodness I have this old Mac to fall back on!
A mate of mine who has only been using Macs for a few weeks has been using a PowerBook G3. We installed Mac OS X 10.4 Tiger on it, and then he got a larger hard drive. He was about to reinstall OS X when I suggested cloning.