Hi Gang,
Good news! I finally got the transfer process locked down.
Forget Ethernet! Too darned complicated and trouble prone.
krissel offered the key clue — purchase a PCMCIA firewire card for the PowerBook.
We had already decided to purchase a backup firewire drive for her.
So now it was a simple matter of developing the right strategy to get it all to work:
1) Insert PCMCIA fw adapter in PowerBook
2) Boot PB and
wait for it to put the icon on the desktop for the PCMCIA card. This is critical!
3) Connect fw cable between PB and fw drive and turn on fw drive
4) FW icons appear on desktop! Magic!
5) Drag files to be transferred to the 'Transfer' partition on the fw drive
6) Dismount the fw icons by dragging to the trash. (critical)
7) Disconnect the fw cable
Shut down PB
Then, on the iMac:
1) Start up iMac if not already on with fw icons showing on the desktop
2) If fw icons don't show up on desktop, power off fw and power back on. Icons should now show up.
3) Open 'Transfer' partition and copy files over.
4) Dismount fw icons. (Critical)
5) Power off fw drive.
I probably have too many steps in there, but it works for now!
This could have been much easier if the PB was a newer model running OS X.
Then the PB could have been connected via firewire mode and mounted directly on the iMac desktop.
But this is a PB G3 Wallstreet sans fw and running OS 9.
Thanks to all who offered suggestions, and especially to
krissel for giving that clue about the PCMCIA FW card. ($20)
WOW!
Thanks again, Jack