I have a C++ application which I’ve just updated to be built using Visual Studio 2012. The original solution was developed in Visual Studio 2010, so I updated the project properties, Configuration Properties | General | Platform Toolset to Visual Studio 2012.

The application is a 32-bit application, everything was built for 32-bit and all worked well on Windows 7, but on Windows XP (which is still used by some of our users) it failed with the “exe is not a valid Win32 application”.

Checking the configuration manager suggested it was indeed a 32-bit application. Running dumpbin /headers app.exe confirmed it definitely was a 32-bit application but XP said no it wasn’t.

Here’s the thing – I hadn’t noticed when setting the Platform Toolset, there was a second option Visual Studio 2012 – Windows XP (v1100_xp).

Changing to this toolset fixed the problem. So 32-bit does not mean 32-bit on all Windows.