My PowerBook G4 (15" 1.67Ghz) is currently on the fritz. I replaced the HD and now it is having problems starting up. I tried to start up the machine off of the install CDs (holding c) but the screen remained black (I hear the start up chime). I finally got it to boot off of the CD but the computer did not recognize the new HD. When I formatted the drive with the disk utility (Mac OS Extended/Journal), the install recognized the disk but there was a red ! saying this drive will not work. So I decided to restart the computer, at which I am back to the black screen and not booting off of the cd drive. Thanks for any help.