Bob calm down and boot to your Mac. Then mount the external hard drive. Then launch /Applications/Utilities/Disk Utility then follow these steps to make that drive to except different versions of PPC or Intel OS X installs.
1. Launch /Applications/Utilities/Disk Utility.
2. In Disk Utility highlight the main part of the drive in the left hand column.
3. In the right hand column, near the top, you will see the tab "Partition", click it.
4. Use the same window pull down and select 1 Partition.
5. (IMPORTANT) Select near the bottom (of the same window) the word 'option'.
6. Select the option to make the 1 partition either accept PC or Intel OS X.
7. Format.
See you must tell the drive to expect OS X not just read and write to it.