Solution:
1. Download the Installer from http://www.quark.com/en/Support/Downloads/
2. Right click on the downloaded Installer package in order to decompress the contents of the package. A new folder with same name as that of the downloaded Installer will be created at the same location.
3. Open the unzipped folder and double click on Setup.exe file in order to launch the QuarkXPress 2016 Installer.
4. Click 'Next' once the installer is launched and follow the instructions on the screen.
Select the Installation type as 'Full Install' and enter your Validation Code.