I usually use MS Visio if I need to make Entity-Relationship Diagram (ERD) or even if I need to make a network model in my class and in my work. This software was very useful to me in my database design class, system analysis and design, and in my network security class last session. MS Visio used an enhance metafile (.emf) format which is originally a File Extension EMZ (.emz). In short, .emz is a zipped .emf files. This is a Microsoft graphic format for Office and Visio.

If ever Windows fails to open the File Extension EMZ, the possible cause of this is that you may not have the correct program installed or, you may have registry errors. What I did before, was I just simply run the drivers update to fix the problem. You can also download for free the driver detective to update your drivers instantly. If you have an editor that will accept .emf files,try unzipping the File Extension EMZ and then import them into the editor, this will also work.