Files with .flow extension can be opened using SketchFlow by Microsoft Expression. This program featured by Expression Studio Ultimate allows you to design prototypes of your ideas effectively, go over these ideas more quickly and focus the client’s attention to the goal of your application rather than go into details too early such as color or font style. You present these prototypes through flowing screens of images, text and diagrams. You will be able to demonstrate your prototypes to your client effectively, letting them visualize the concept and for them to evaluate and give their feedback. It lets you and your client to keep track of your ideas from raw concept to finished product in a faster pace. To run Microsoft Sketch Flow 4.0, you should have one of the following: Microsoft® Windows® XP with Service Pack 3 or Windows Vistaâ„¢ or Windows 7 or Windows Server 2008 operating system using a computer with 1 GHz or faster processor.