How can I retrieve the "CLSID_SeparateMultipleProcessExplorerHost", without querying the Registry? Is there any Win32 API to take the "CLSID_SeparateMultipleProcessExplorerHost" as parameter and give me the GUID of it.
The string "CLSID_SeparateMultipleProcessExplorerHost" does not exist in the Registry, or anywhere else. It is strictly the name of a compile-time constant value of {75DFF2B7-6936-4C06-A8BB-676A7B00B24B} that is defined in the Win32 SDK for use in source code only. The name is stripped out during compiling.
Typically, if you pass a CLSID value to ProgIDFromCLSID() at runtime, you will get the CLSID's associated ProgID name, which can be passed to CLSIDFromProgID() at runtime to retrieve the CLSID. However, this particular CLSID does not have an associated ProgID, so that is not an option.