As a result, when I reboot the computer in OS 9, I am greeted with the alarming news that all of the partitions contained on the drive on which my OS X partition resides cannot be recognized, and I am offered the usual choice between re-initializing and ignoring the message. Obviously, I choose to ignore the message in order to rescue my data.
Read the rest of the article for details on how to safely make the drives usable again...
One of the characteristics of Hard Disk Speed Tools, and the one which prompts me to choose it over Apple's Drive Setup, is the ease with which one may delete and create partitions. Of course, the utility for this <i>par excellence</i> would be FWB's Hard Disk Toolkit--except for the annoying fact that FWB always seems to be several months behind in developing drivers compatible with new Macintosh operating systems. Another very nice characteristic of Hard Disk Speed Tools is its ability to "take over" a drive that has been formatted with another disk formatting utility.
When I receive an alarming message such as the one I have just described, I do the following: I restart from a bootable CD, open a copy of Hard Disk Speed Tools that I have either on my boot disk or on another volume that can be recognized when I boot from the CD, and select "Update drivers". When I perform this operation upon the drive that contains the OS X partition, I am informed that the update cannot be made because the drive was formatted by another utility, and that the only course open to me is to "take over" the drive. Usually, a drive takeover can take anywhere from half an hour to a couple of hours. However, in this case, when I specify a takeover, I am immediately greeted with the message that the takeover operation is complete. I then, just to be safe, choose "Update drivers", and then restart in OS X. Once I have done this, I have no further problems--that is until and unless I have to install OS X again!
(Needless to say, I'm sending a copy of this note to Apple's OS X feedback site.)

