Okay, your /etc/network/interfaces file should look like this
# The loopback interface
auto lo
iface lo inet loopback
# The first network card - this entry was created during the Debian installation
# (network, broadcast and gateway are optional)
auto eth0
iface eth0 inet dhcp
Okay. After doing that, you have to issue the commands
ifdown eth0 and then
ifup eth0.
This should reset your ethernet card address.
ifconfig should give you a proper address now. You can try pinging your router
ping 192.168.1.1. If that is all okay, then your ethernet card is set up okay.
If you can't access
www.google.com, then that is a DNS problem and you have to edit
/etc/resolv.conf to look like this:
nameserver xxx.xxx.xxx.xxx
nameserver xxx.xxx.xxx.xxx
You may have to figure out from your ISP which nameserver addresses to put in here.