Network / DSL modem problem

Hi,

I'm trying to help someone with a Dell laptop running Windows XP that
has suddenly developed a strange problem.

It was working fine, but was then unplugged from the modem to be used
in another location for a PowerPoint presentation (on the laptop's
screen). When brought back and the Ethernet cable was plugged in again,
the laptop couldn't see the modem. The Network Control Panel shows
"network cable unplugged" under it, but the cable is plugged in
properly and no settings have been changed (at least not manually).

I've even tried:

- both the modem and laptop have been restarted,

- the Network Control Panel has been 'disabled' and
then 'enabled'

- a different cable,

- a different modem (which I think works properly,
but was the only other one I had available to try).

All with no success and no change. I've even tried installing the
drivers to use the modem via its USB connection, but the computer
doesn't see the modem that way either.

At the moment the laptop is using a dial-up modem instead while we are
waiting for a replacement modem to arrive from their Internet provider,
but I'm not convinced that the modem is really the problem.

I'm wondering if anyone has any other suggestions that I can try on
Monday.

Thanks.