cannot ping one pc on network

[Headtheball]

I have a small home wireless network consisting of my pc connected via
ethernet cable to wireless router, My sons PC and my wireless laptop. When
all are switched on My Pc responds to ping cmd on xxx.xxx.x.2, the router
responds on xxx.xxx.x.1
the laptop on xxx.xxx.x.3 but my sons pc with the ip xxx.xxx.x.4 times out
and doesn't respond. It also doesn't appear in workgroup computers. If I try
to view available network pcs from my laptop all enabled devices are
recognised. What is causing my son's pc not to be recognised?

 

[Lawrence Abrams]

I have a small home wireless network consisting of my pc connected via
ethernet cable to wireless router, My sons PC and my wireless laptop. When
all are switched on My Pc responds to ping cmd on xxx.xxx.x.2, the router
responds on xxx.xxx.x.1
the laptop on xxx.xxx.x.3 but my sons pc with the ip xxx.xxx.x.4 times out
and doesn't respond. It also doesn't appear in workgroup computers. If I try
to view available network pcs from my laptop all enabled devices are
recognised. What is causing my son's pc not to be recognised?

Can the xxx.xxx.x.4 machine access the internet? Is it possible they have a
firewall installed?

What version operating system is the xxx.xxx.x.4 machine?

If windows xp, use this tutorial to see if the built in firewall is enabled:

http://www.bleepingcomputer.com/forums/index.php?showtutorial=40