Since there is no information about any other released versions, you will need to try to save the file to another format or version. Many applications have support for saving to a certain file format for different versions. If it's not possible, then I am afraid you can't open it because there is no other Winkis version released. You might want to get in contact with the company who developed this application. It's possible that customers may benefit from support (download resources, manuals, etc).