You need FileMaker Advanced installed on a system running windows. Perhaps Parallels?
Before you try producing the runtime, just open the file with FileMaker on the windows system and examine/test it thoroughly. Text displays differently in windows and thus you may need to adjust your layout designs. window management is different if your solution opens mutliple windows. FilePaths are diferent in windows than in Macs.
Those are the most obvious differences, but check your file out before trying to make runtime for Windows.
Many thanks for your help with this. I have now managed to create a runtime pc version. I now need to work out how I can distribute it to my friends.