I'm thinking that it is the hard drive. Though Disk Utility throws up no errors or warnings.

Used Clone Carbon Copier to copy my G4's (the one I'm use as my daily driver and am using to post this) hard drive to my friend's hard drive.

Now, here the funny part.

From turning on from a power down state, it gets to about to boot and throws up a kernel panic window right before desktop. BUT THEN IF I reset the machine with Apple-Option-Power Button to get out of the Kernel Panic, it boots normally.