A few months ago, while running Tiger on my Mac Pro, I installed a new additional hard drive and then installed Leopard on that new volume, calling it "Leopard". The boot volume choice seemed to be a bit flaky the few times have rebooted while installing, but I went with the flow and didn't pay any attention to it. Today, I installed a bunch of new software in this sequence: On Leopard: I installed Windows Office for OS X and two immediate subsequent software updates for that, bringing me up to 12.1.4 I did Software Update for OS X, bringing me up to 10.5.5 I then had to restart. When my system rebooted, Tiger came up. (I wasn't quite paying attention). Then, I got a prompt for Software Update again, so I did that (for Tiger). I clued in that I was running Tiger (missing the obvious fact that my screen background was not Leopard.... duh), when I saw the Java 10.4, Version 7 update. Then, my Tiger BackUp kicked in, so that took a DVD write, and an Adobe Reader update. Phew. So, then I go into Tiger System Preferences and set the boot volume to Leopard, and restart. Tiger comes up again. I go back into Tiger System Prefs and select Leopard to boot from, and this time I lock the preferences, and restart. No joy - Tiger comes back up. Each time it confirmed to me that it had selected Leopard as the boot drive. So, I really liked Tiger, but now I'm stuck in it. What to do?