Are you sure, that you are conneected to the internet (google may be loaded frome cache)? I.e. can you access your email, does another browser work or can you at least ping somthing out there? If not, than your internet-setup maybe broken. Otherwise your firefox settings are wrong: Did you use a proxy-server or something else that is a little bit special? Some more info were great.
Btw. "Win XP" is not really a distribution ;-)