If you open Dewesoft and you get the error that package.pc or options.opt file is missing all you need to check is to which System folder Dewesoft is looking at. 

Often if Dewesoft was uninstalled Dewesoft left registry entries which contains information about the system folder. To know to which system folder Dewesoft is looking, all you need to do is go to  Files and Folders section of the settings.

After you know the location you can copy the files packages.pc and options.opt there. Dewesoft should now open any without problems.