Systems not display in workgroup_LAN network

Hi Friends,

I am learning windows 2003 server networking & administaration. Actually I want to set up windows 2003 server network. So that initialy I am trying to set up LAN network with 4 systems (windows 2003 server enterprise edition - desktop /xp sp2 - 1 desktop, 1 laptop/ Vista sp2 - 1 laptop)

1) In windows 2003 server installed system, i cant get display of other systems in workgroup. But, in workgroup of other 3 systems windows 2003 server installed system displaying well.

2) in the same LAN network I cant access VIsta sp2 installed laptop, when I try to access thru other 3 systems, the MsgBox shows the error

" \\SAHADHA (system name) is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions. Logon faulure: the user has not been granted the requested logon type at this computer. "

PLease help me to solve this problem.