Usually it's not necessary to reboot a client when DHCP changes your IP
address, but usually this change also never happens...

In our environment we use DHCP for NT servers and workstations without =
any
problems. The client gets an IP address lease from the DHCP server =
(with a
validity of 1 week in our case). As there's no need for the DHCP server =
to
change the address of a client when the lease has expired, we never get =
such
changes when the client is online. Even when the lease is expired and =
much
time has already passed by, the client usually gets the old address =
again as
the MAC address of the network interface card is remembered. When you =
change
the NIC, you likely will get a new IP address, but in this case a =
reboot
should have happened.

Best regards,
Michael