GUID Locations

GUIDs appear in the following locations:

• .reg files — When an application is created, usually one or more .reg files are created. The .reg files contain the GUIDs for the classes that an application exposes. These GUIDs are added to the registry when you run Regedit.exe to register the classes, or when you register type information with LoadTypeLib.
• The system registry — Contains the GUIDs for classes in multiple locations. This is where OLE and applications get information about classes.
• .odl files — When objects are described in an Object Description Language (.odl) file, a GUID needs to be provided for each object. Compiling the .odl file with the Microsoft Interface Definition Language (MIDL) compiler or the MkTypLib utility places the GUIDs in a type library, which usually exists as a file with a .tlb extension. If a GUID is changed in an .odl file, you should run MIDL or MkTypLib again.
• .tlb files — Type libraries describe classes, and this information includes the GUIDs for the classes. The .tlb files can be browsed using the Tlbrowse.exe sample application supplied with OLE.
• .h files — Most application developers will declare class IDs (CLSIDs) for their classes in a header file by using the DEFINE_GUID macro.