Did you make the direct connection to NID - to determine if
noise is from internal or external source? Demonstrated is
one modem that tends to be more noise resistant (has a better
DSP algorithm) than the other. Test still does not identify
source of noise and resulting disconnect. You still have
disconnects. Therefore you are not yet identifying reason for
failure. Long before we discuss fixing the problem, first
concentrate on identifying the problem. Hyperterminal has
always been a powerful tool for identifying a modem verse line
problem in part because it is so simple to use and because it
provides fundamental facts without the summarizations (basic
data removed) from Windows.

Caroline wrote:
To be complete, I have an update:

I switched to the integrated modem ("56K AC-Link Voice Modem")
two days ago. I also switched the telephone access number I use
with Earthlink. My rate of disconnects has gone down
considerably--only one in the last 2.5 days, vs.
half-a-dozen or more daily in the recent past. (My time on the
computer and typing messages did not change notably in the last
2.5 days.)

I'll switch back to the external modem soon and see if the
problem was a "crowded" (or otherwise deficient-in-some-way)
access number.