Not Able to ping ISP DNS in Windows 2000 Server system

Hi

I have windows 2000 Advance server system in domain. I am able to browse domain and access other systems of network. I am also able to connect to remote Server and work on application. I have defined correct IP, Subnet mast,Gateway and DNS and able to ping IP's and and also Gateway of ISP but when trying to ping DNS of ISP it shows Remote Time Out.I am not able to surf internet. Other systems of the network XP/2000 are able to connect to internet(ISP) and surf web without any hussle. Till yesterday this system was also working fine

Pls. help me to solve this problem

Regards
Siddhpal Singh Patel