I had a problem with Leopard defaulting to Clean Install rather than Upgrade on my Imac G5 1.8 pre intel 10.4.10. It gave me a warning during the early part of the install(where you start to see the bar that indicates time remaining) stating that installation could not be completed on this Mac. In the process, it obviously started to overwrite my Tiger HD. For a couple of days, I had no HD access and every method to solve it, always came back with my HD not being seen by any methods. I then used Disk Warrior 4 in the affected machine, making sure the C key was held on start up just to force it to be the home disk, and after a longish intro, it enabled me to rebuild the directory of my HD without any loss. I now have the same Tiger HD in all its glory. As I have seen some similarly frustrated users post their woes, I thought this might save a few others. Certainly saved me.