can ping the internet but IE,or other browsers will not connect to the internet.

This may be bcos of proxy setting

go to IE tools options and check proxy setting .make sure either it is
unchecked or if it is checked the proxy setting is correct

no , it has no proxy. It was working ok, then one day this started.

Hi,
  I was just looking arund when ur question came up.
  If u r able to ping the ip for e.g-66.94.234.13 and yahoo.com both
than ur arec onnected but cannot browse .If only one oings but not
there other than there is a problem with dns settings.

 But if ur able to ping both than -

1)either there is a firewall inbuilt like in xp or there is a firewall
ionstalled .hich u need to disable and than try out.
2) Also this problem also arises of spywares and adware that are
installed on the computer.
3)also please check the winsock files which are so vital but people ignor them.
4)if ur using a router,please check if u r able to connect only using
the modem or not .
5)and also check the proxcy settings 
6)and choose never dial a connection.

Hope this will answer ur problem.