You may need to go into the file association dialog and setup the DDE (
Dynamic Data Exchange ) option. That usually has something to do with files being opened in their associated apps.
In the image below i have all the dialogs open that you need to, to get to this setting. You'll notice a %1 at the end of the application path in the example image. Make sure you add the space before the "%1".
Your file association windows should look very much the same as this.
If you open any Folder, then the TOOLS menu, then "Folder Options...", "File Types...", then click the "Advanced" button... you'll get to where these dialogs show in the example image.
You may be using a different version of Windows so a couple of these notes may differ from mine. In that case, any questions, just ask.