You can use Screen class to get the screen resolution.
This sample is taken from MSDN:
' This method will adjust the size of the form to utilize
' the working area of the screen.

Private Sub Button1_Click(ByVal sender As System.Object, _
   ByVal e As System.EventArgs) Handles Button1.Click

   ' Retrieve the working rectangle from the Screen class
   ' using the PrimaryScreen and the WorkingArea properties.
   Dim workingRectangle As System.Drawing.Rectangle = _
       Screen.PrimaryScreen.WorkingArea

   ' Set the size of the form slightly less than size of
   ' working rectangle.
   Me.Size = New System.Drawing.Size(workingRectangle.Width - 10, _
       workingRectangle.Height - 10)

   ' Set the location so the entire form is visible.
   Me.Location = New System.Drawing.Point(5, 5)

End Sub