The following prerequisites are required:
.NET Framework 2.0 (XP, Vista, Windows 7)
.NET Framework 4.5 (Windows 8.x, Windows 10)
Even if these components are already installed, the automatic launch of the Sudoku-application does not work (the web server seams not to be configured adequate). Therefore download these installation files (XP, Vista, Windows 7) or these installation files (Windows 8.x and Windows 10) and unzip the archive and double-click the setup.exe file and the sudoku.application file respectively if the correct .NET Framework is already installed. Once installed, the application will check for, download, and install updates automatically (internet connection required).
And if you like the Sudoku application, I would be pleased about a little donation.
Due to internal variations the current version of Sudoku is not compatible with versions prior to version 22.214.171.124. If you have already installed an older version of Sudoku you must uninstall the older one prior to installing the current one (using the regular "Add or Remove Programs" control panel of your Windows installation). The automatic update will not update older versions of Sudoku to the current one!