I nearly always put two [seldom more] os on every machine and if possible on separate disks. On older macs this is generally 9.2.2 & tiger. On a pc generally recovery console, ghost 8.0, and XP. And I always keep data on it's own partition on macs, windows and linux. An a little over the top example, my QS has two drives: big one for music with a small tiger rescue partition at the beginning , and a fast smaller drive with swap, tiger, applications, home, and os 9 in that order.

If it's not obvious why, this allows me to screw things up and just reinstall the os. Also allows diskwarrior to work fast from a different partition. Also protects my data short of disk failure. Also lets me in if the main os just checked out.

2simple