Need Help!

My firm have a Windows server 2003 standard and Win XP Pro. users.
Server is a domain controller I we have a DNS DHCP File Server Print server...
My problem is when I open a my network places/entire network/microsoft
windovs network/my group i cant see some users/computers. When I search for
thet computers I find them easelly and I can access then. But their are not
in the list entire network. How can i put them in thet list ? Thank you very
much.