A Globally Unique Identifier or "GUID" exists within the GDI.wif file for each VTS application. This GUID is assigned to the application when it is initially created. The GUID helps VTS to distinguish between different applications.
By definition, no two GUIDs are assigned alike, although it is possible that a copy of an application can reside on one workstation, thereby causing VTS to alert you to the presence of duplicate GUIDs. Instructions on remedying this situation can be found in the topic Duplicate Globally Unique Identifiers (GUIDs).