Is the floppy ejected without comment (an error message) or accompanied by the floppy-disk-with-X icon? The first may be the result of a corrupt (or no) System on the floppy, and the second the result of the System on the floppy's being incompatible with the Mac model, or older than the PB 'thinks' its present System to be.
What the Mac takes as its present System may be garbled because of the failed installation, so you should try the old 'four-fingered salute' (command-option-p-r) immediately after you switch on, allow three extra chimes, and only then push in the floppy disk from which you are trying to start up. If that doesn't work, try again with the shift key held down until the splash screen shows with the extensions disabled (or off) message. Yes, I know that there are already very few extensions (usually only the CD-ROM enabler in System 7) present on the floppy, but the technique has worked for me.
If you still get no joy, revisit your floppy disk itself. How was it prepared? Later Systems than 7 on another Mac may not be decompressing the disk image correctly, so try to make the floppy in another System 7 Mac.
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What the Mac takes as its present System may be garbled because of the failed installation, so you should try the old 'four-fingered salute' (command-option-p-r) immediately after you switch on, allow three extra chimes, and only then push in the floppy disk from which you are trying to start up. If that doesn't work, try again with the shift key held down until the splash screen shows with the extensions disabled (or off) message. Yes, I know that there are already very few extensions (usually only the CD-ROM enabler in System 7) present on the floppy, but the technique has worked for me.
If you still get no joy, revisit your floppy disk itself. How was it prepared? Later Systems than 7 on another Mac may not be decompressing the disk image correctly, so try to make the floppy in another System 7 Mac.
de