Manny, right-click on a .XAR file and pick Open with > Choose another app.
In the 'How do you want to open this file?' window, scroll down to the bottom and pick More apps.
Navigate to the DesignerPro.exe file ("C:\Program Files\Xara\Xara Designer Pro+\DesignerPro.exe") and select that.
Finally, tick the option to make it the default.
Second finally, do the same for any .WEB file.

Acorn