Dell Vista PC keeping diapup connection alive

I added a Dell Vista PC to the LAN, keeping all the defaults. My
dialup connection would time-out after no Internet requests for a
7-minute period. Now, with the Vista connected to the LAN, it
constantly stays online as long as the Vista machine is up and
running. I turned on logging (on the Win 2000 proxy PC) to monitor
activity which shows no activity/requests for the Vista PC. If I
unplug the Vista PC's Ethernet connection, the connection times out as
it should. So, I know the Vista machine is pinging or something else.
I uninstalled Norton Internet (that came installed with the PC) and
installed Antivir as a replacement.