Description
The OPC channel and the tag browser in WinCC need network services to establish a connection to an OPC server. You can achieve this even without a physical network. For this you install the "Microsoft Loopback Adapter" as described below.

Instructions
 

Operating system	Procedure
Windows NT	In the Control Panel you select "Network", then select "Network card" and click the "Add" button. From the list displayed you select "MS Loopback Adapter" and install it. You need the Windows NT CD-ROM for this procedure.
Windows 2000	Detailed instructions are available from Microsoft at this link: http://support.microsoft.com/kb/236869
Windows XP, Windows Server 2003	Detailed instructions are available from Microsoft at this link: http://support.microsoft.com/kb/839013
Windows Vista	Select the Classic view and then proceed as for Windows XP.
Windows Server 2008	Select the Classic view and then proceed as for Windows XP.
Windows 7	Select "Start > Control Panel > Device Manager > Network Adapters". Select "Action > Add Legacy Hardware" and then proceed as for Windows XP.