Question : Laptop can ping but does not respond to ping.

So, I've got 3 computers in my home network.  2 are running vista (1 laptop, one desktop), 1 XP (laptop).  I'm trying to set them up to share files and have run into a snag.  One of the computers (The one running XP) will not respond to ping.  I can see it in the "Network" on the Vista computers but when I ping the both the ip and the computer name, I get "request timed out".  This happens from both of the vista computers.  I've disabled my windows firewall, and the windows security center is showing that "you have no firewall enabled" and this is still occurring.  The XP machine has no problem seeing or pinging the vista machines, and they are all in the same workgroup.  Both laptops are connecting via wireless adapters.

When I boot into safemode on the problem computer, it will respond to ping with the windows firewall enabled.

Answer : Laptop can ping but does not respond to ping.

Defiantly sounds like a firewall enabled on the XP machine. If you are sure the windows firewall enabled, are there any others such as McAfee,, Zone Alarm, or perhaps a security Suite such as offered by Symantec?

Though it is not designed to resolve your problem, downloading and installing the update from the following link helps XP machines to work better in a Vista environment.
http://www.microsoft.com/downloads/details.aspx?FamilyId=4F01A31D-EE46-481E-BA11-37F485FA34EA&displaylang=en