Update: You can convert compressed ISO images (.ciso files) using this method, too…
If you need to translate a Wii DVD image from the newer .WBFS format (which has lovely sparce-file support) to an old-school .ISO image, well you can jolly well do so with Wii Backup Manager! Now, WBM is a really useful program so congrats to the author (xzxero) – but it uses non-standard GUI elements in that it uses what looks like the category list as a second main-menu, and this makes it a little non-intuitive to use. But in fairness to the author, the download page has a tutorial (which I didn’t find until after completing this post!). Still, it’s easy enough once you’ve figured that out. The entire conversion process goes like this:
1.) Grab yourself a copy of Wii Backup Manager. Version v0.3.5 beta 1 is the most recent version available at the time of writing, and although it’s Win32 only, it works fine in VirtualBox…
2.) Extract and launch it
3.) From the Files tab, click on what looks like the Add category title, select Files and go pick a .WBFS image from the navigation dialogue box
4.) Still in the Files tab, tick the checkbox to the left of your .wbfs image, and then click on what looks like the Transfer category title and select ISO..
5.) Pick where you want the converted .ISO file to be created and click the [OK] button