Background:
This occurs due to incorrect default program settings.

Solution:
1. Highlight/Select any .xml file.
2. Right click on the file, click Open With>> Choose Default Program>> Browse>> Navigate to C:\Program Files (x86)\QXA>> Choose Quark.XA.Startup
3. Click Open and check the option 'Always use the selected program to open this kind of file'.
4. Click OK.