Is that OS is Windows XP? If so, try to check local Area Connection is Enable r not. To do this u need to open Control Panel –>Network Connections , Right click on Local Area Connection. U can see Disable option if it is enable, r else u can see Enable if it is Disable.
And also make sure that DNS server ip addresse, Default gateway adress are correct. U can able to ping the Gateway.
U can get this info by simply typing ipconfig/all at the command prompt.
If ur accessing the internet through proxy server, ensure that proxy server ip address is correct and u can able to communicate with the server.
I hope this will work for u… If u have any concerns pls let me know..
additional from me
If your OS is 98, try to check TCP/IP in Control Panel –> Network Adapter. If there TCP/IP more than 1 you can delete TCP/IP adapter.