Alas, i am back,

So, i finally got around to fixing my old PowerBook g3, turns out it was the CPU.

So the 400mhz cpu was broken so i bought a 333mhz off of ebay, and im thinking great, problem solved, just need to borrow a hard drive.
So i took a hard drive out of another lombard with os9 on it, plug it in to my lombard, and start it up; it chimes, goes to grey, then flickers, and just stays on a grey screen. Nothing else. The hard drive starts up and everything. I tried another hard drive/cable, same thing.

Without the hard drive, it boots up normally and asks for an OS.

What could be causing this?