What is wrong with this network configuration (Ubuntu 10.04 LTS)?

I have used Nokia siemense networks modem provided by BSNL to access net in windows XP. Recently I have installed UBuntu 10.04 LTS but here I am unable to access internet though it is expected that ubuntu 10.04 LTS should automatically connect to net. I have tried by best by configurring network connection but with no success so far. Can anybody please comment on what is wrong with the configuration?
The details are: 1.Net Connection ->wired->auto etho (enabled)->edit
here in the new window that appears, I keep MAC address, MTU unchanged (automatically detected).
IPv4 setting: method automatic (DHCP).
DHCP client ID no idea what to put here. keep blanck as it is?)
I leave Routes unedited
I check the "connect automatically" option, then click "apply"

2. Next I go to DSL->add->wired->MAC address {which address to put here? same as before or leave blanck as it is or the MAC address as reported by 192.168.1.1 which is different from what is automatically detected in step 1}.
IPv4 settings-> method, automatic PPPoE
DSL-> here I give same username and password which I used to put for connecting to bsnl broadband in windows XP.
PPP setting-> check use MPPE.
also check for the connect automatically option. then click apply.

3. In firefox I use networks->settings-> no proxy (even auto detect proxy does not work.) Or should I actually set proxy? what should that setting be?
4. Finally I am unable to connect to internet through BSNL broadband using above modem in ubuntu 10.04 LTS. Please suggest what modifications are required. Surprisingly If I open 192.168.1.1 in firefox I get identical reports for DSL status, LAN, etc as these were in windowws XP. Apparently nothing is wrong only the internet can not be connected.

ack'ed very late reply but if things are ok then ignore the content or else ...
first things first - if you had your modem/router up and running at the time of installing ubuntu 10.04 it would have automatically detected the network(eth0/wifi), this is used for the apt utility. If not it can easily be achieved using the network-manager(gui).
checkout:- Ubuntu 10.04 – Networking Configuration Using Graphical Tool Ubuntu Linux Technical blog

if dhcp doesn't work opt for the static/manual

where the entry should be of the form(iff router falls in 192.168.1.X network)
address:- 192.168.1.Y
netmask:- 255.255.255.0
gateway:- 192.168.1.X

enter the dns server: 8.8.8.8
8.8.4.4
or use the opendns
this should work
if not
as you have indicated that the router webpage is accessible.
then paste the output of ifconfig and ping