What does it mean when sdt says settings.txt cannot be found and how do I fix it?
A little more information would help narrow down the problem
What mod did you try to install?
Did it have instructions? If so, have you followed them?
Did the mod come with a "<ModName>settings.txt" file? If so, did you put it in the "Settings" folder located in your main folder? (The one with the mods folder, Loader.swf, SDT.swf ect.)