Because SimCity 4 doesn't run quite right under Tiger, I decided to install Panther on a partition on an external drive just for playing SC4. Anyway, after partitioning the drive, including a 30 GB partition for Panther, I installed Panther. It wouldn't boot for some reason, and Tiger's Disk Utility reported an unrepairable error with the partition. So, I installed Panther again. This time it booted fine, and I proceeded to update to 10.3.9 with Software Update and rebooted with no problems. I then installed SC4, and played it for quite a while, creating two cities. I also installed a couple other apps for use when booted in Panther. When I was done playing, I shut down, disconnected the external drive, and then booted the machine back up (into Tiger of course). After a while I decided to go back to Panther and play SC4 some more. Here's where things get weird. I opened Startup Disk and was surprised to notice that it reported OS X 10.3.4 on the external drive, as opposed to 10.3.9. Figuring it was just something weird with Startup DIsk, I selected the external and rebooted. When the machine booted up again, I was greeted with the Set Up Assistant. Again I thought it might just be a weird hiccup, so I quit out of it, but I had to set up my login account again. After logging in, I found that the OS was only at 10.3.4, and there were no apps (including Sim City) installed whatsoever. It's as if the drive magically reverted to exactly the state it was in right after I installed Panther in the first place. This is after I had installed 10.3.9, rebooted and confirmed that it had installed, as well as played SC4 for several hours, during which I quit the game and restarted it with no trouble loading my cities. I'm updating to 10.3.9 again now, then I'll reinstall SC4. Does anyone have any hypothesis as to what may have happened? I'm absolutely sure that the partition on the external that I installed Panther on to is the same one that I've booted from every time, so it's not a matter of just getting confused with which partition is which. I mounted the external in Tiger and Spotlight didn't find any of my SimCity files anywhere on the whole system (including all three partitions and my internal drive). The strangest thing to me is that 10.3.9 was not only installed, but previously booted, then the OS reverted to 10.3.4, but otherwise was fine.