Are you on a local network? If so, can you ping other hosts on the local network? If not, it's a TCP/IP or NIC card problem. If you can, then your TCP/IP is installed and working properly, so that's not the problem. Is there a proxy server or firewall on your local network? If so, this is why you can't ping. Most proxy servers and firewalls block ICMP packets, including pinging. Try using tracert rather than ping and see if it works.
If you're not on a local network, then possibly TCP/IP is not working - try pinging 127.0.0.1 (the loopback address) to see if this works. If not, uninstall and reinstall TCP/IP.
If none of the above is true, then you have some other type of configuration problem or possibly a network problem.Would need more details on the hardware involved to go any further on this. Hope this helps!