I believe that VFP defaults to upper case extensions, but will automatically change the case of the scx file's entire name, including its extension, to whatever was typed in the command window it for editing. If you open the existing file myform.scx by typing MODI FORM myform, it will saved as myform.SCX, and if opening it with MODI FORM MyFoRm.ScX, that mixed case will be perpetuated.