That did it!  Thank you!  Now that I've got the thing off of life support I can start in on the chicken-and-egg problem of getting software onto it.  I have an AppleCD 600 that is refusing to cooperate.  I'll see if CD-ROM Toolkit helps there, the CD drivers from 7.5 aren't doing it.

If only OS X could still write to HFS volumes.  I've been creating disks from disk images in Linux so far.