For many years I have used a program called Expert Personal Roots (EPR) to develop my family tree. The software was originally used with Windows 3.1. Over the years, I have upgraded to Windows 95, Windows 98, and then Windows XP and each time I saved and copied the EPR folder to the new version of Windows. The program worked perfectly in Windows 95 and 98, however after upgrading to Windows XP whenever I attempt to run EPR a message appears: ‘Divide by zero or overflow error’ and the program will not run. In response to this problem, I installed Virtual PC 2004 so I could run other operating systems within the Windows XP ‘host’. The guest operating systems installed are Windows 3.1/DOS 6.22, Windows 95, and Windows 98 SE. I have copied all the EPR files onto the Windows 95 and Windows 98 SE guest operating systems, and it works fine on each of them. However, when I copy the files to Windows 3.1 (in exactly the same way) the same ‘divide by zero’ error message appears, as in Windows XP, and EPR will not load. Why doesn’t EPR work on Windows 3.1, even though the program was originally designed for this system?

Since you have been able to get EPR running under Windows 95 and 98, I am assuming your question about why EPR will no longer run under Windows 3.1 is for academic interest, rather than a need to have the program working. That said, this is quite an interesting question! It would be useful to have EPR running under Windows XP, so we will first cover ways to accomplish this, as it may be of interest to other readers who are also experiencing similar problems when running older programs under Windows XP. Fortunately, Windows XP has a function which allows programs to be run in a compatibility mode for a specific operating system. There are two ways you can set the compatibility mode for programs, either using the Program Compatibility Wizard, or by manually setting the mode for programs. To find instructions on both of these methods, go to the ‘Start’ menu > ‘Help and Support’. In the window that appears, click ‘Fixing a problem’ (in the right-hand pane). Then, click ‘Application and software problems’ followed by ‘Getting older programs to run on Windows XP’. From here you can find a link to the Program Compatibility Wizard and also instructions on how to manually specify the compatibility setting for programs. A web version of this article can be found at www.microsoft.com/windowsxp/using/helpandsupport/learnmore/appcompat.mspx. Unfortunately, Windows 3.1 or DOS is not offered as an option for running programs. Therefore, you will need to specify a compatibility mode of Windows 95, 98, NT or 2000.

We now need to discover why the program no longer works under Windows 3.1. My best guess is that after copying the EPR directory between various generations of Windows, concluding at Windows XP before copying back to Windows 3.1, some of the files may have been slightly altered by the later versions of Windows (e.g. due to differing functionality and/or file system handling in the newer versions of Windows) thus making them incompatible with Windows 3.1. This could be further exaggerated since Windows 3.1 was a 16-bit system, whereas Windows 95 and later are 32-bit systems. As a workaround, you could try reinstalling EPR on Windows 3.1 from the original disk, check that the program works and then copy the EPR data files (and only the data files, make sure you do not copy the program files) back into the EPR directory.