Hello stzatzop;
To open a S5 program you need Step5 (or a third-party application like S5 for Windows). You cannot open a S5 program with Step7. The conversion utility (Covert S5 to S7) can only be used effectively if you know the details of the original (S5) program and of the process yuou want to control. The converter will translate about 80% of the program correctly; the rest you must handle yourself, and the missing blocks may be critical to your application, especially if you are doing it blind.
Hope this helps,
Daniel Chartier