Hello and welcome to our forums,
If your old installer is MSI-based, you can get its Upgrade Code. This code can be used in the "Upgrades" page in order to set the new package to upgrade the old one. With this method the old package is uninstalled automatically and silently right before the new installation starts.
You can check our
How to upgrade an older version of the package article.
If your old installer is not MSI-based, check the
How to upgrade an older version of the package created with another tool and it is not MSI-based tutorial, where everything you need to do is explained.
If you can't get this to work, you can send us the .AIP (setup project) file and a download link for your old installer (created with Setup Factory) to
support at advancedinstaller dot com and we will try to assist you.
Best regards,
Liviu