Macintosh starts up to Open Firmware or gray screen after upgrading hard drive

• When the computer starts up, it displays a gray screen. The desktop never appears.
• When the computer starts up, it shows a white screen, with text that includes the phrases, "Open Firmware" and "default catch".
• When the computer starts up, you may see an alert message such as "unimplemented trap" or "segment loader error".
• When you try to install Mac OS X on the computer, the hard disk is dim and can't be selected in the installer.

This only happens with certain Macintosh computers that originally had a hard drive smaller than 8 GB, and that have now been upgraded with a hard drive larger than 8 GB. These computers include:

• iMac 233 MHz
• iMac 266 MHz
• iMac 333 MHz
• Power Macintosh G3 Desktop
• Power Macintosh G3 Mini Tower
• Power Macintosh G3 All-In-One
• iBook
• iBook (FireWire)
• PowerBook G3 Series

If you have just upgraded the hard drive on one of the computers listed above and you see this issue occurring, here's how to get everything running smoothly again:

1. Back up all your data. (This is a good thing to do regularly, not just now!)
2. Start up from your Mac OS installation or restore disc.
3. Use Drive Setup (in Mac OS 8 or 9) or Disk Utility (Mac OS X) to partition the drive. Make the first partition smaller than 8 GB, and any other partitions can be any size you want.
4. Install the Mac OS in the first drive partition.