Hi,
As the site owner you can always access your data. In the web services panel you can make a complete backup of the database.
Go to http://(your site here)/config and log in. Use the lost password link if you've lost it.
Once you log in, in the top group of links - left side - select "create/restore backups" and on the resulting page you'll see that you have options to backup all or part of your data. If you're looking to migrate to a different forum system you'll need the database which is the bottom check box, and if you have any attachments you'll need the web files, which is the top check box.