Private Declare Function SetWindowPlacement Lib "user32.dll" (ByVal hwnd As _
      IntPtr, ByRef lpwndpl As WINDOWPLACEMENT) As Integer
 
    Private Const SW_SHOWNORMAL As Integer = 1
 
    Structure WINDOWPLACEMENT
        Dim Length%
        Dim flags%
        Dim showCmd%
        Dim ptMinPosition As POINTAPI
        Dim ptMaxPosition As POINTAPI
        Dim rcNormalPosition As Rect
    End Structure
 
    Structure POINTAPI
        Dim x%
        Dim y%
    End Structure
 
    Structure RECT
        Dim Left%
        Dim Top%
        Dim Right%
        Dim Bottom%
    End Structure
 
    Function restorewindow(ByVal hwnd As IntPtr) As Boolean
        Dim place As New WINDOWPLACEMENT
        place.showCmd = SW_SHOWNORMAL
        place.Length = System.Runtime.InteropServices.Marshal.SizeOf(place)
        Dim ret% = SetWindowPlacement(hwnd, place)
        If Not ret = 0 Then
            Return True
        Else : Return False
        End If
    End Function
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim hwnd As IntPtr
        For Each p As Process In Process.GetProcesses
            If Not p.MainWindowTitle.IndexOf("Windowname") = -1 Then
                hwnd = p.MainWindowHandle
            End If
        Next
        restorewindow(hwnd)
    End Sub