cannot visit internet websites from Ubuntu

Hello
I am new to ubuntu ( in fact new to linux). i am not a software engineer but need a laptop for my everyday work.
I use an ethernet (LAN) conenction to at home and office for connecting to internet. Surprisingly the internet works perfect in my office with ubuntu but not at home.
after installing ubuntu, i did not make any changes to any settings and just plugged in my LAN cable and internet got working in office. but when I use LAN cable for internet at home, I am unable to.

I read through a lot of forums and similar problems and tried the suggested solutions but in vain.
I added the static IPv4 IP address, IPv4 subnet mask and IPv4 default gateway in the respective fields. But I am unable to add any address to DNS server.
I lso have windows VISTA on my laptop where internet works perfectly.

Please help.

LG