681
i believe backup just backs up your whole database, like the phpmyadmin export options, or phpnuke's backup tool
as far as reinstalling, why not just go into phpmyadmin, select the tables that you would like to keep the content for, export (back them up)
then empty the database, run the XOOPS install, when it's finished, import the backed up tables
to make life easier, when you back up (export) the certain tables that you want to keep, make sure that you select 'Add Drop Table', if that option exists
as far as reinstalling, why not just go into phpmyadmin, select the tables that you would like to keep the content for, export (back them up)
then empty the database, run the XOOPS install, when it's finished, import the backed up tables
to make life easier, when you back up (export) the certain tables that you want to keep, make sure that you select 'Add Drop Table', if that option exists