There is a rare issue with Zorin OS 5 that after installation it fails to recognize any other operating systems that you may have on your computer and doesn’t list them in the boot up menu (GRUB). We have created a bug fix for this issue which can be downloaded here. To fix the issue extract the “grub-fix.zip” file by right clicking on the file and selecting “Extract here”. Then double click on the extracted file and run it in terminal mode. It should prompt you for a password and then it will run the fix. Changes will be applied after a system restart.