If you turn off the firewall and you can ping when using safe mode, make sure no other security software running.

Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net 
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com 
 Good Morning

 I have a laptop running on our corporate network. For some unknown reason it
 is not possible to ping this laptop. I have started it in safe mode with
 networking and suddenly its pingable. I have re-installed the network
 drivers, disabled many services & drivers using msconfig but still cant pin
 point the problem. I have also tried it on another network port and IP adress
 to no avail. Windows firewall is disabled (it was on SP1 when i first looked
 at the issue) and I have already re-installed the network card. If i put a
 new disk with a basic image into the laptop it works fine which rules out
 hardware / xp compatibillity issues, network issues. I am sure a rebuild will
 fix it but this laptop is going to be a pain to rebuild....any ideas??  The
 way that it works fine under safe mode is really bugging me! arrrrrgh!

 Many Thanks

First guess would be third party firewall or firewall-like security software
which does not run in safe mode.

Doug Sherman
MCSE, MCSA, MCP+I, MVP