Thanks for sharing detailed information about your concern, @anthgav.
Updating the QuickBooks 2005 to R19 is unavailable. The product was discontinued and your current system no longer supports this Desktop version.
You have to upgrade to continue working with your company data. Aside from that, some add-ons can help easily manage your business, available only on supported software.
I recommend visiting our website for the updated pricing and exciting features: https://quickbooks.intuit.com/uk/desktop/.
Our Community site has all the needed information if you wish to upgrade to the latest version. Here are supporting articles for your reference:
Please let me know in the comment section if you need anything else. I'm here to keep helping. Have a good one!