How do I remove the pre processing stylesheet Structured Application Designer

I was experimenting with a pre processing stylesheet for a DITA 1.3 task in the Structured Application Designer and would like to remove it now because it doesn't work, but I can't figure out how to in the dialog box. I tried deleting the path, but it reappears when I open the designer. I have looked in the various structapps.fm files, but the path is not there. How can I revert everything to the default settings?