If you want to install Visio for Enterprise Architects, you must first install Visual Studio .Net. However, if you really do not wish to install Visual Studio, you can do a "mini" install by deselecting every Visual Studio option (e.g. Visual Basic .Net, C#, etc.) and proceeding with the installation wizard as if you had selected some options. This will, in effect, load only the bare minimum of Visual Studio files and trick the Visio installer into thinking that Visual Studio is installed.