I'm not exactly sure what you mean, but if you want to start another form in your application you can do this by:
yourFormName form = new yourFormName();
form.ShowDialog(); //This will lock all your other forms until this dialog is closed
form.Show(); //This will run the form and keep your other forms unlocked aswell, if you close your main form though, this one will close aswel.
Or if you would like to run an executable file, you can just use the System.Diagnostics.Process library.
Since this is a standard windows executable though, you could have also used Process.Start("calc.exe");
I want to start other application (xyz.exe)
I have tried with Process.Start, but I keep on getting error messages, presumably because of wrong path. Remember that I 'm working on smart device, so my path is something like "My Device/Program Files/..." or am I wrong...