It never hurts to try power cycling, but that doesn't seem to be the problem. The drive *sounds* like it's spinning up correctly and as expected, not to mention it's mounting on the desktop without any more intervention. It simply sounds like your problem is the drive is not bootable to me, and that's entirely a software/formatting issue.

Click to expand...

Well, not so fast, young bird.

I have had drives that were slow to spin up (as I mentioned before, either due to the infamous stiction problem that afflicted many drives of their generation, or from bearing grease that had gotten sticky with time). They frequently would not boot. However, I could mount them if I booted off of a floppy, just as described by the OP. If I did the power cycle trick, I could get them to boot reliably. So I wasn't speaking theoretically. I have directly observed this phenomenon.

That said, I do agree that it's a long shot, but it's such an easy experiment that it's worth a try.

Much more likely is a need to reformat at 3:1 interleave, and reinstall a clean Plus-compatible OS.