put this code in a button or timer or whatever you want!!
Dim ScreenSize As Size = New Size(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
Dim screenGrab As New Bitmap(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
Dim g As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(screenGrab)
g.CopyFromScreen(New Point(0, 0), New Point(0, 0), ScreenSize)
screenGrab.Save("C:\" & Label1.Text & ".jpeg")