problem with some net sites

Hello!
Any help would be much appreciated.
You see, i have a VERY annoying problem.
There are some sites, that when i type in the URL, all i get is the
standard "The page cannot be displayed" site.

The problem is, the sites i am tying to go to include:
www.google.com
www.topcoder.com
and some other sites that should work, and do on other computers.

Any suggestions?
(BTW, this is on an old computer, Celeron 500, running win 98, but i don't see that this would be a problem in this case)

You haven't mess with your hosts file, have you?

VERY CURIOUS
i posted this yesterday, and today i go on, and everything works fine after months of not doing do.....
:( confusing

Anyway, i'm not sure what you meant by 'hosts file', but i guess i hadn't messed with it