When i installed window 7 ultimate on my laptop, i wont be able to browse any internet sites.?

Someone said its only mozila firefox that works without hitch but i find that difficult to believe. Even though i was able to browse with the mozila firefox , is there anything/setting to do to make internet explorer work on Windows 7 or whether the version is the problem. Pls advise. Because of this problem, i had to remove the windows 7 ultimate and install vista ultimate.