ok then, in that case, i don't remember what script takes you through setting
up your network, but the config is stored in /etc/network/interfaces, and
you want the following two lines:
auto eth0
iface eth0 inet dhcp
and then it should Just Work. if you want this to be a system that
works nicely in multiple network environments with different requirements
(like a laptop that goes between home and work), you can find lots more
information from 'man interfaces', though if you have dhcp in all locations
you should be golden as is.