Hi,
guess it wont be that simple. First of all you need to know where your pc's get there IP addresses from. Do you use DHCP on your network? Take a look at the DHCP configuration then. You can use ipconfig /all on windows to get some more information about the network configuration. On Win7 you can also disable ipv6. Pinging a computername will only work if you have DNS Service on your network or you manually create a host file entry. Just give us some more information about your setup. An output of ipconfig /all would be nice and the command you used to ping them. If you are on linux the output of the following commands would be interesting: ifconfig, cat /etc/resolv.conf and route -C
Cheers,
RBA