It sounds like it has to do with your windows file associations.
If you go to the file in a windows directory, and then right click and select "Open With" what does it show as the default program?
I suspect it shows edrawings at the default program.
It should show SW.
Try changing one or more of the file types.
How did you try to open the file?
By opening SW and using the Open command to select?
By dragging the file into SW?
It may require a registry fix if you can not re-associate the files.
You can also see if Windows saved a "restore point" at some time shortly before the problem started - but be carefull, if you made any other necessary changes to Windows things after that time they will be gone.
Thanks for your answer, you are correct the file association was showing edrawings as the default program. However is would not let me select anything else, so I did a SW repair, then could select SW Launcher. Now everything is happy again.
Thanks for the help