SetupApi

I am looking for the declaration for the windows api dealing with USB.
Several internet postings suggest that the file I am looking for is
SetupApi.pas, but I can't find that file.  In particular I am looking for
the declarations of HidD_GetHidGuid, SetupDiGetClassDevs,
SetupDiEnumDeviceInterfaces, and the dependent structures.  There are
probably other api calls I'll need once I get into the implementation.  Can
anyone tell me where these are declared?

Thanks,

Roy Cooley