Windows 3.1 build 103

Windows 3.1 build 103 is the official RTM build of Windows 3.1, released on 6 April 1992. The Checked/Debug compile can be obtained by installing the Windows 3.1 SDK and running a batch file in the SDK folder.

Switching from free to checked/debug compile
To switch to the checked/debug compile, you will need to install the SDK. Launch setup, and on the page where you select the components, select only "Debug binaries". After installation, select "Debug Windows 3.1" in the "Windows SDK" program manager group. After a restart, Windows will start, but a watermark appears at the bottom right of the screen saying "Debug Windows 3.1". This means that you are now running the checked/debug compile of this build.

To switch back to the free compile, select "Non-Debug Windows 3.1" from the "Windows SDK" program manager group. After another restart, you are back.