|I see. The problem is that with Explorer, when you right-click on a file, and choose "Open with..." it allows you to choose which program to use for files of that type. Unfortunately, it saves that information in its own registry settings, instead of creating a new file association. So I guess this is what happened on that laptop.|
I don't know why Microsoft chose to use two different ways of associating file types. It complicates things unnecessarily. But then I'm not surprised, as Microsoft has a track record of complicating things.
What you want to do is create a proper file association. Here is what I've got:
As you can see, I've downloaded the standalone executable version of the Flash Player, so .swf files open in their own Flash Player window. I guess if you want to open them in IE, replace the above with the pathname to IE (IExplore.exe somewhere under Program Files).