I'd be grateful if someone could put me right on my attempts to get
either of these scanners working. I was a bit surprised as both
manufacturers seem to support linux for printers.

using ubuntu 7.10

referred to
https://help.ubuntu.com/7.10/printing/C/scanning.html#id2509682

regarding PSC500 HPLIP says YES it is supported
hplip.sourceforge.net/.../combined.html

regarding xerox 2400 [i didn't pay for it so i'm not shedding tears! -
it would just make a smaller repalcement for the PSC500]
www.sane-project.org/sane-backends.html
the 2400 is listed saying the chipset is the GL646_HP and may be added
to the genesys backend

a] perhaps i miss a setting somewhere to get a scanner working in linux
b] how can add it to this genesys backend... [i'm not sure quite what
it means by backend!]