Cannot ping laptop

[Taz]

I've got three machines connected via Wi-Fi to the same router: 2 laptops (running XP Pro SP2) and a Dell Axim PDA. All of the machines successfully get an IP address from the router (196.168.x.x) and can surf the Internet. However, I cannot ping any of the machines. I am trying to ping a machine using its IP address (192.168.x.x) but I just get a 'Request timed out." message.

Any ideas?

Edit: i can only ping the router's IP address of 192.168.0.1 from the laptops.

[Taz]

I eventually found the problem: Windows XP SP2 firewall was blocking the ping.