Hi Phil,
If the site is on the same server, you don't need to use DNN Backup.
Steps:
1 - Make sure you have a dev domain pointing to the server. You will need that to run the dev site;
2 - Copy the site files to the dev domain root folder on the server;
3 - Backup the DB using SQL Server Management studio;
4 - Restore the backed up DB with a different name to SQL using SQL Server Management studio;
5 - On the copied site files, change the connection string inside the web.config to point to the newly created DB;
6 - On the copied DB, go to PortalAlias table and replace the live domain with the dev domain;
7 - On the copied DB, go to PortalSettings table and look for DefaultPortalAlias. Replace the live domain with the dev domain;
With that you should be able to run the cloned site;
Once you are ready to make dev the new live you can:
1 - Go to IIS and switch the site root folder from the live site to point to the dev site;
2 - On the copied DB, go to PortalAlias table and replace the dev domain with the live domain;
3 - On the copied DB, go to PortalSettings table and look for DefaultPortalAlias. Replace the dev domain with the live domain;
In short I think this covers it all.
Best regards,
Aderson