I also partition HDDs into as many as three for use in older Macs and Systems, but I name them either according to purpose or or by size: as Storage or Quantum 350MB, or the like, being careful to have no two volumes with the same name (and size, if that is included in the name). The Startup Disk CP is not particularly smart about distinguishing between potential boot partitions so, even if you are assured that the copy of Startup Disk is not corrupt, you are testing its concentration by presenting it with multiple choices.
1) Not until OS 9 does Startup Disk list in the CP the System Folders, as opposed to available HDD partitions, for startup;
2) earlier Systems display all available volumes in the CP, whether they each have a valid System Folder or not, and highlight all the volumes of a given disk together.
To have some chance that the desired startup volume will be used:
1) if you are simply backing up complete System installations on the same partition or drive, remove Finder from each inactive System Folder into its enclosing Folder;
2) deselect all volumes in the CP by clicking outside them in the CP window, and then click only the volume from which you wish to start up, close the CP, and then restart.
Even then you may need to do some fiddling when you wish to use a different System, and to be prepared for the sheer fag of starting up from the last-used System Folder or disk partition, making a change in the CP, and then restarting from your current choice of System. There are other wrinkles that may be employed, such as:
1) the four-fingered salute (command-option-shift-delete) to get Startup Manager to ignore SCSI 0 and use the next valid SCSI ID up the series, or
2) the five-fingered salute (command-option-shift-delete-number), where 'number' is the SCSI ID of the desired drive (now you know why 'c' to select the CD-ROM drive was such a good idea),
but none of these is guaranteed of success with older Startup Disk CPs, sitting and sucking their thumbs in puzzlement when they are confronted with choices far beyond their designed capacities.
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