Forcing .Net assemblies to use the 32-bit processes on a 64-bit platform

When a Windows application has been compiled using the “Any CPU” target register there is still a way to forcefully start the application in a 32-bit context.

This can be accomplished by using the Microsoft (R) .NET Framework CorFlags Conversion Tool from the Microsoft Windows SDK for Windows 7 and .NET Framework 4.

Using the CorFlags.exe (navigate to: C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\CorFlags.exe you can toggle the 32-bit/64-bit awareness of the specific application.

First we need to figure out the actual compiled/build properties of the executable.

C:\CorFlags.exe application.exe

Microsoft (R) .NET Framework CorFlags Conversion Tool. Version 3.5.30729.1

Copyright (c) Microsoft Corporation. All rights reserved.

Version : v2.0.50727

CLR Header: 2.5

PE : PE32

CorFlags : 1

ILONLY : 1

32BIT : 0

Signed : 0

To enable the application only for a 32-bit processes:

CorFlags.exe Application.exe /32Bit+

To enable the application to address also the 64-bit processes:

CorFlags.exe Application.exe /32Bit-

When you executed the command using the **/32Bit+** parameter you will see a subtle but very important change.

C:\CorFlags.exe application.exe
Microsoft (R) .NET Framework CorFlags Conversion Tool. Version 3.5.30729.1

Copyright (c) Microsoft Corporation. All rights reserved.

Version : v2.0.50727

CLR Header: 2.5

PE : PE32

CorFlags : 3

ILONLY : 1

32BIT : 1

Signed : 0 s