It is very simple to understand the programming i have done in this example.
The Program first gets all running current process if the count is greater than one that means there are more than one instance running so it gives an error and closes the application
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
If Process.GetProcessesByName(Process.GetCurrentProcess.ProcessName).Length() > 1 Then
MsgBox("This is a Single instance Applicaton " & vbNewLine & "* Another Instance is Already Running", MsgBoxStyle.OKOnly, "Single Instance Application")
Regards Hefin Dsouza