How to Connect 2008 Windows Server to a Shared Workgroup
1. On Windows server 2008, open gpedit.msc from the start menu (this will prompt for elevation). Then open up Computer Configuration, then Administrative Templates, then Network, then Link-Layer Topology Discovery. On the two settings in the right pane, right click and select the properties. Make that it is enabled and configure the options to Allow operation while in domain, for a workgroup, enable the public network option make sure it is not disabled on private networks.
2. Windows server 2008 use a discovery protocol called Link-Layer Topology Discovery (LLTD) to query other devices on the network to determine how the network is organized. Link-Layer Topology Discovery (LLTD) Responder component is not always installed on the Windows XP-based computer. Check if LLTD installed on the Windows XP clients is the latest. If not, you have to uninstall them and install the updated one.
3. Run 'services.msc' and Enable Computer Browser service on Windows Server 2008 servers, which is disabled by default.