Where are the settings for which applications handle what file types stored within IRIX? Have a issue that .tiff and .rgb files are no longer set to Image Viewer and want to force re-set it.
I am not sure about the settings for all file types, but at least the image type associations are handled, I believe, from: Desktop -> Customize -> Utilities.
The "Desktop User's Guide" (attached) may also reveal more, but I haven't sorted through it