static extern int OleRegGetUserType([In] ref Guid clsid, uint dwFormOfType,

  static extern int OleRegGetUserType([In] ref Guid clsid, uint dwFormOfType, out IntPtr pszBuff);

    int nResult = OleRegGetUserType(ref clsid, (uint)USERCLASSTYPE.USERCLASSTYPE_FULL, out pszBuf);