There's no problem with them seeing each other's file system if that's what
you mean. However, the NTFS system will by default have much stronger
security, assigning user permissions and file ownership and these things can
interfere with access. That said, for the most part the problem is one of
how the network is set up.
First, it's a good idea to use the XP Network Setup Wizard and to run it all
machines on the network. Second, when running the wizard, you need to be
sure that any firewalls or other security is turned off on all machines as
this will interfere with network setup.
Third, many home networks connect through a hub. During the wizard, the
user is asked how this computer connects to the Internet and very often they
will select the response "Through a Network Hub." An incorrect answer at
this point will stop all communications between computers after setup is
complete. Usually, the correct answer is "Gateway."
The above addresses the major issues that can cause communication problems
on home networks.