There are a couple of obstacles that I see in your process (and I'm no
computer expert so I'm certain there are better ideas and information out
there than mine -- but here's my two cents).

1.  You stated that you have a 600 scanner which means the highest resolution
you can scan a photo in is 600 dpi (dots per inch) which is not the greatest
resolution (print quality is 1200 dpi).  But if you've set your scan at any
less than 600, you are certainly getting poor quality images.  So yes,
changing the resolution will help, but your scanner is limited to 600 dpi
although your software could scan higher with different hardware.

2.  Photoshop also has other settings that affect the quality of the scan i.e.
color vs black and white image settings (color is much more clear - even if
the original image is black and white).  Linedrawing vs photo setting (line is
good for just that -- lines, graphs, charts, etc. -- for anything else I'd
recommend the photo setting).

3.  Your Photoshop manual should provide sufficient info and guidance to
selecting the best settings for your project.  I don't know of any "bible"
that's going to provide better or faster solutions.

4.  Remember that the image quality is affected by the original scan settings.
You can't go in and make a poor image clearer once it has already been
scanned.  You'll have to re-scan the image to improve the output.

5.  What you see is what you get.  If you improve the images on screen, people
will be able to print the better images, although I'm certain there must be
some control features to lock out printing -- I don't know how that part
works, but I'm sure the Mac online folks could assist you there.  You can talk
to a rep online through their web site.

6.  In terms of saving the image so that it fits the size of your screen,
again that will need to be part of your scan settings.  In Photoshop, when you
initially "place" the scanned image on your screen, there is an arrow prompt
that allows you to draw the size of the frame for the scanned image (or you
can set the image size manually).  You need to set this frame at the max size
you desire -- you can always shrink the image later if you like, but enlarging
an image loses detail and quality.  Again, check your manual for better
instructions.

7.  Yes, you can scan multiple images, then cut them indivdually.  But the cut
and paste process is a pain so I don't know if it really saves any time or
frustration.  But if you'd like to try, simply scan the images (put space
between them when you lay them out on the scanner so that you don't lose edges
to cropping during your cut).  Save the scan multiple times under different
names -- one for each of the individual images.  Then simply go into each
saved file and cut out the images you don't want in that particular file using
the crop and erase tools.  Of course, update your saved file after cropping so
that you are only left with the desired image remaining.

Finally, 15,000 images is going to take up a lot of space no matter what you
do.  Since you're using a zip drive, I'd go for the best quality, but you
might think about buying those zip disks in bulk!  I hope this helps.  Good
Luck.

Marissa C. Weaver
Executive Director
America's Black Holocaust Museum
Milwaukee, WI