Replacement hard drive not detected

I recently got a used Powerbook G4 with the knowledge that the hard drive was probably bad. After a week of troubleshooting, and lots of time looking through Mac forums, I gave in and bought a new one. After installing it, the computer will not see it. I am trying to install the original OS (Tiger I think) and when I get to the screen where to choose a destination, the hard drive does not appear. So then I go to Disk Utility, and it is not there either. The old hard drive was in both. So now I am stuck. Any advice???

Thanks from a novice Mac user with just enough knowledge to be dangerous, but not enough to solve my problems!