Thank you all for all your replies.  I did go to the Archivist list, and
there was a thread similar, but it hadn't been resolved. I am contacting
the original querent to see what she might have learned off-list.  The
following is to try to explain my original request, since it seems to have
confused people.
All of the 'scan only' images we own have been attached to Past Perfect
cataloging, and the CD/Zip files are either the archival back-up copies, or
the
original image files from the donor (each donor's gift images that I have
scanned from their originals) are archived
on a CD under their accession number).  All of the images attached to PP
are also backed up, a folder at a time, on CDs.  That is why the original
nomenclature query-what do I call these electronic donor files in my Past
Perfect
cataloging? ROM, CD/DISK, ZIP (?)
One of my largest image 'scan only' files comes from the local newspaper's
morgue.
They were kind enough to let me scan the photos from their photo morgue (2
owners ago, in the 1980s, one seller did not convey the previous photo file
and it vanished) for our collection.  The original photos are at the
newspaper; we have the scans & backups of the scans on CD. At least if the
paper is sold and the photo morgue lost again, these 650 images will be
preserved.
The worry I have is that later on these electronic only files will be
unreadable by future programs.  That is why I felt it might be prudent to
print copies of the 400 dpi TIFF archival images, just in case. Also, when
I get time, 
all files on Zip disks will go on either CDs or DVD (my computer does not
have a DVD drive)
 because the Zip drive seems to be like the Dodo...disappearing.  
Again, thank you for helping.  This one-band band in a small town in the
Shenandoah Valley appreciates it.  Mary Thomason-Morris, Archivist, Clarke
Co. Hist.

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