There is a two-step system to associate files without icons to default programs:
1. in prefs/DefIcons you define how to identify a file.

- deficons.png (6.14 KiB) Viewed 7819 times
On the right you see the comparisons done to the file or its contents in order to identify its type and on the left in the name field you see the file type which is associated. In the example it is jpeg. This means that all files which are identified by the comparisons will show the icon which is taken from env:sys/def_jpeg.info.
You also see in the list browser that there is a hierarchy in file types. This means that if env:sys/def_jpeg.info does not exist, it tries env:sys/def_picture.info. And if this does not exist, either, it tries env:sys/def_project.info.
2. once an icon file is selected, the default tool specified in the icon file is used to open the file.

- iconinfo.png (6.84 KiB) Viewed 7819 times
Note that the entire mechanism only applies to files which do not have an icon on their own.
So if you have a file called mypicture.jpg and another file in the same directory called mypicture.jpg.info, then this mypicture.jpg.info is always used, no matter what you enter into env:sys/def_jpeg.info.
In order to use deficons for mypicture.jpg, you have to delete mypicture.jpg.info.
In order to restore all def icons you need to copy all def_xxxx.info files from your installation CD to envarc:sys.
Finally, please don't mix up Workbench with Windows Explorer. Workbench only shows icons, it does not show files. Workbench is not good to execute file operations like copy, move, rename and so on. If you need to do such operations which make it necessary to see all files (usual files and icons), you should either use the Shell/CLI or or a directory tool like DirOpus.