If you have an older version of Zorin OS and wish to update to a newer version please follow this guide:
1. Backup all your valuable data that you might have to an external media or the internet.
2. Download Zorin OS .iso file which you want to install and burn it to a DVD or get a Zorin OS DVD from the Premium page.
3. Insert your Zorin OS disc into your computer and let it boot from it.
4. Open Start > System > Administration > GParted and delete the ext4 and linux-swap partitions and click apply.
5. When the partitions have been deleted, open "Install Zorin OS" on the desktop.
6. Complete the installation procedure. In the partitioning phase select "Install Zorin alongside [your other operating system]" if you have a dual boot setup with another operating system or "Erase disk and install Zorin" if your computer has no other operating system installed. This should install to the space which was previously freed.
7. Copy your valuable data back to your new Zorin OS installation.
You should now have a newer Zorin OS system with all your files back.