If you cannot see other workgroup computers on the network on a
XP based PC this entry may helps.The following criteria should be
true for your PC in this case: - The PC resides on a network / - The PC
is a member of a workgroup / - No firewall is enabled / - The PC can ping
other PCs in the same workgroup / - Other PCs in the same workgroup can
ping your computer / NetBIOS over TCP/IP functionality is enabled.

Microsoft writes this issue may occur if the computer is configured to use
p-node mode for name resolution.To check if the Pc is configured to use
p-node.mode do the following :

Run an ipconfig/all in command prompt.Check the Node Type entry at the top
section of the output.If there stands Peer-Peer the Pc
is running in p-node mode

To resolve this issue navigate to :

-HKEY_LOCAL_MACHINE\System\CurrentControlSet
\Services\NetBt\Parameters\

Delete now in the right pane (if present) the entries :

NodeType
DhcpNodeType