Yes ..!It is possible to hide files in ur nokia s40 phones without any software..How. .?
STEP-1:Create a folder of any name like xyz.
STEP-2: Move the files you want to hide.
STEP-3: Now just add the extension .jad like if you have xyz folder rename it to xyz.jad
STEP-4: Now create another folder in same directory with the same name but different extension of .jar (example xyz.jar)
STEP-5: Now your main folder will not be shown.
To see the original folder rename the visible folder and your hidden folder will appear.