Paul,
While I have not personally used them, I would recommend that you take a look at the backup products from evotiva.com. They are available at Snowcovered.com.
The Evotive.BackupScript is said to do this:
"full site backup & restore (no matter if the database is local or remote), even from scratch (no DNN running): the database (any size is supported, all BLOB columns are supported) plus all files and folders on the site (including \portals, \bin, \desktopmodules, web.config file, etc.). The database is scripted as standard, commented and readable .SQL files!. The module can build all the datababase objects and recreate the data."
My reading of this is that the database is "backed up" with scripts so that you can get at all of the data, should you need to do that.
Now, one problem that you'll encounter with moving a forum is that forum posts are identified with users so that you can't simply move posts without also having user names being moved to the new forum. This could be a problem if you don't want to do that.
There appear to be some "for dummies" books related to SQL. You want to make sure that you get a book that refers to the MS SQL variant. I have a copy of "SQL Server 2005 Programming" that I find useful. It's a little more advanced than "dummies" books, but is accessible. As a starter, there is also a nice tutorial on SQL at
http://www.intermedia.net/support/s...qltut.asp. It will get you through the basics.
As for getting a copy of a single site, I'd probably suggest that you make a copy of the entire installation, move it to localhost, and then delete all but the portal of interest. Then, you'll probably want to make sure that you go through the database, and make sure that all references to other portals are actually gone and not just marked as deleted. Then you could use the evotiva script to generate a complete backup.
Transferring users is going to be one area where you'll need to be particularly careful. The "users" table in DNN doesn't separate users by portal. There are other tables where this is done. So ... some careful work will need to be done here, but not impossible.