DOCUMENT:Q159408  11-JAN-2001  [vbwin]
TITLE   :PRB: "Error in Loading DLL" if Calling Multimedia API Functions
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:WINDOWS:4.0
OPER/SYS:
KEYWORDS:kbmm kbAPI kbVBp kbVBp400 kbGrpDSVB kbDSupport

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The information in this article applies to:

 - Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0 
 - Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
 - Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SYMPTOMS
========

When you call multimedia API functions from 32-bit Visual Basic for Windows
using the Declare statements retrieved from the 32-bit API Text Viewer, the
following error message appears:

   "Error in loading DLL"

CAUSE
=====

The error occurs because the 32-bit API Text Viewer incorrectly uses the Declare
statements for Mmsystem.dll, which is a 16-bit DLL.

MORE INFORMATION
================

A 32-bit program cannot directly execute functions in a 16-bit DLL. A thunking
layer is required. The thunking layer allows you to load a 16-bit DLL and place
the processor in 16-bit mode so you can execute the appropriate code. However,
Visual Basic for Windows cannot implement a thunking layer and its use is not
supported. There are two ways around this behavior:

1. See the following article in the Microsoft Knowledge Base that describes how
   to call the 16-bit Mmsystem.dll functions:

   Q141939 : How to Create an OLE Server to Implement Thunking

2. Call the functions from Winmm.dll, the Windows 95, Windows 98, Windows NT,
   and Windows 2000 library for multimedia. Winmm.dll is a 32-bit library that
   supports multimedia services. This method requires the proper Declare
   statements for Winmm.dll.

REFERENCES
==========

For additional information, please see the following article in the Microsoft
Knowledge Base:

   Q141756 How to Play MIDI Files Using API Calls from Visual Basic

Additional query words:

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Keywords          : kbmm kbAPI kbVBp kbVBp400 kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400
Version           : WINDOWS:4.0
Issue type        : kbprb

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Copyright Microsoft Corporation 2001.