>>How can we protect (modifications/visualizations) from pgms such Xtgold, File Manager, Visual´s browse, etc.) the DBF´s DBC´s tables of datas, since the applications have to get to see the directory and tables where they are installed for running?

If you want to avoid user using external utilities to write into your DBFs, you may want to try XiTech encryption utility. But, since you are using Visual FoxPro, if the table are REALLY Visual FoxPro, then these utilities won't be able to even read the data.