Cannot ping client I can see is connected to my router.

Hi all, first time poster here. I have a laptop that I can see is connected wirelessly in the console of my SMC wireless router and it can connect to the internet without issue. However any ping requests I make from a desktop time out using both the IP and the host name. I have checked the software on the laptop, and can see no Firewall software other than the standard XP stuff. I have another laptop with a similar config that I can ping/access fine. What have I not checked?

Thanks in advance!