The site could not be found error on browsing

Hi all!
I have internet access on my laptop. I can chat via MSN Messenger.
I receive emails in Outlook.
I cannot browse the internet. Any website that I type in my browser is giving me an error message stating that the site could not be found. Whatever website I type in my computer, it can not be found.
Whatever browser I used, I still get the same problem. I tried with Internet Explorer, Google Chrome, and Mozilla Firefox, but I cannot browse. I have Windows 7 installed on my laptop.
My laptop also has a fixed IP address.
Please help.
