TCP/IP Corrupt?

I am on an NT 4 network. I can get on the internet, and the loopback test works, but I cannot ping my own IP or others on the network. I have uninstalled, rebooted, reinstalled TCP/IP but to no avail. I have a decent nic in a decent Dell Dimension XPS T600r. Any thoughts on what to do? How do I install a fresh version of TCP/IP without too much crap?