Doubleclick Enroute 5 file opens a new program window

Hi.
I wonder if anyone has a solution to this: When I want to open a Enroute 5 file with a doubleclick, it results in a new program window opening to show the file, instead of opening it in the already started program window.
This is cumbersome as I often use filesearch and such to find the correct file I am looking for, and instead of opening it with a doubleclick or ENTER, I have to note the file placement and open it "manually".
I suspect there is a way to edit the registry to fix this, so if anybody has the recipe to do this I would appreciate it if you could share it here.

Enroute 5/Windows 7

Best regards
Tony

I don't know the answer to this problem, but I have struggled with it for as long as I've used Enroute versions 3 up to 5.1. Same behavior in Windows XP and Windows 7. To make matters worse I've found that if I accidentally double click an Enroute file and Windows opens a second Enroute window, it partially crashes Enroute and it starts not working correctly. I then end up having to close and reopen all Enroute windows to get it working right again. Complaining to SAI has not helped. I do not know if the behavior is any better with Enroute 6 or Windows 10, but I doubt it.

Probably the best thing to do is disable Windows' association of the .rou file extension with Enroute so that Windows Explorer will no longer even try to open an Enroute file directly. If I need to use Explorer to find something I then copy the path to the file (shif+right click on the file, then click "copy as path" in the popup menu) then paste that into the file open dialogue window from within Enroute.