The disk set you describe was issued in two sets: either as a pre-Power Macintosh 10-disk set or 11-disk set for installing onto a Power Macintosh. The error is occurring because the installer script on these disks is trying to install 7.1.2 resources over your active System 7.5 software.
Follow these steps to manually install the Powershare Server software on a Workgroup Server 6150, 8150, or 9150.
Step 1
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Start up from the Workgroup Server CD and run the installer for PowerTalk. (To bypass the currently selected start-up device, start or restart the computer while holding down the Command-Option-Shift-Delete key.)
Step 2
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Insert the PowerShare Server Install Disk 3 and install the PowerShare Catalog Server and the PowerShare Mail Server applications.
Step 3
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Place aliases to the PowerShare Catalog Server and the PowerShare Mail Server applications in the Startup Items folder of the System folder.
Step 4
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Restart your Macintosh computer to make the PowerShare Server software active.
Step 5
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Setup the server as per the instructions in the "PowerShare Collaboration Servers System Manager's Guide."
NOTE:
The PowerShare Admin program is on the Powershare Server Install Disk 2.
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