Okay, so I have a G4 iMac which was running 10.3.9 just fine, and I erased the hard drive and installed Tiger on it, and it went through the whole start up thing, and then when the screen turned blue, the beach ball started spinning, and then it stopped spinning and it was frosen. We tried everything. We zapped the P-ram, we tried to eject the install CD, we tried to boot up on the install CD. We're lucky if the screen even lights up. So then we tried Fire-Wire disk transfer mode. I plugged it through firewire into my iBook, and the drive showed up, but before I could run any tests on it, the iMac shut down by itself. It doesn't stay on long enough for us to do any thing with the drive. Now, we finally tried to just boot it up and eject the CD again, and we got this: "System Failure: cpu=0; code=00000001 (Corrupt stack) Latest crash info for cpu 0: Exception state (sv=0x2DD1DC80) PC=0x000AB8F8; MSR=0x00001030; etc etc etc" It went on for a long while. It all appeard on top of the Apple logo screen. What can we do?