Little setup info needed. Wireless, Ethernet, what type of network. Also, laptop is able to access the network? Or no? If no, check for latest drivers, or uninstall the NIC in device manager and reboot. What OS are you trying to connect from? Same OS (XP) or 2000, etc? How is this setup, P2P, via Router, switch, hub, etc... let me know. Going to go workout now.

Ethernet network. Laptop can access all resources on the network. I cannot ping the laptop fron any machine, XP, 2000, nt4 etc.....
Out of about 400 pcs this is the only not responding to ping.

Try this to reset TCP/IP in XP:
Click Start -> Run -> CMD <Enter>
At the prompt type:
NETSH INT IP RESET C:\IPRESET.TXT
<Enter>
Restart the computer. If this doesnt work, uninstall TCP/IP from network protocols, restart, and then reinstall. Hope this helps. Also might be the winsock file at fault, this is a repair utility you can try:
http://members.shaw.ca/techcd/WinsockXPFix.exe

GL

Simply go to device manager and disable your LAN driver and enable it again, hope it works.

Regards
Rajkumar RM

One obvious question, can this laptop ping any other network device?

Are there any other firewall/security suitess installed (i.e. symantec, mcafee, avast)?

Is tcpip the only protocol installed? Are you perhaps accessing resources using something else? (ips/spx)