So I swapped out the hard drives in my Power PC G4 (let's say HD#1 and HD#2) and put them into my new Intel quad core Mac. When I put them in, I upgraded HD#1 to Snow Leopard. HD#2 had Tiger (10.4.8) on it already and I wanted to keep it that way. HD#1 worked fine with 10.6.3. Well, I wanted to boot up HD#2 (Tiger) and the computer didn't recognize it when I restarted using the "Alt" button. So I did some research and found that i needed to upgrade to the Intel version of Tiger in order for it to work. So I did... well, then I tried to start up HD#2, it makes it all the way to the status bar, then when the desktop picture pops up, it hangs. No icons nor does the dock appear. I have to press the power button in order to do anything. Disk utility says the drive "seems to be ok" etc... but every time I try to boot HD#2, it just hangs on the desktop picture. it get's worse. Ok... so I used Disk Warrior to rebuild HD#2, and it was still hanging on the desktop. Well, I got tired of dealing with it so I switched the startup disk BACK to HD#1 (Snow Leopard)... well... now I get the gray screen with the apple then it turns into that gray 'No' symbol (-pictured below only in gray-). I used the Disk Utility from 10.6 disk and it gave me the 'Hard Drive seems to be ok' message but then afterwords said "Updating boot partition as required" ... Still didn't work. ... Now I am at a loss. so please HELP ME!