Thanks! After determining which of the multiple software CD's would provide Disk Utilities that I could open and use (the computer's original OS 9 install disk) it was a very simple process to get things working again. Only problem I encountered was the unavailability of a version of AOL desktop software (yes, my 86-year old father has dialup service) that will operate w/the OS 10.2 used on this machine. I made a phone call to AOL, and they said that they would ship an installer CD to him ASAP....and to try that. We will see.... Anyway, thanks for all of the advice--this was the first internal disk drive I ever installed and it literally was so simple to do I thought I must be doing something wrong. :-)