Running a C# application as 32-bit on a 64-bit machine

Right click your project, and select properties.

In properties, select the build tab. Under platform target, select x86.

Hit Ctrl+Shift+S to save all files, right click the solution and select "Clean" to get rid of old binaries. Any builds after that should be 32 bit

Command-line form:

corflags application.exe /32BIT+ 

Here's how I did it when we couldn't change the existing code from Any CPU to x86 due to a ClickOnce limitation:

Create a 32-bit (x86 must be checked under project properties) 'launcher' application (Windows Application but not form):

static void Main(string[] args)
{
    // Load the assembly    
    string directory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
    string assemblyName = Path.Combine(directory, "YourAnyCPUApplication.exe");
    Assembly assembly = Assembly.LoadFile(assemblyName);
    assembly.EntryPoint.Invoke(null, null);
}

Add the following code to the Main method in the Any CPU project:

if (IntPtr.Size == 4)
{
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    // etc...
}
else
{
    // Launch application in 32-bit mode
    System.Diagnostics.Process.Start(Path.GetDirectoryName(Application.ExecutablePath)
                                     + @"\Your32BitApplicationLauncher.exe");
}

I hope this helps :-)