Public Class Form1
Public Sub ShowDesktop()
keybd_event(VK_LWIN, 0, 0, 0)
keybd_event(77, 0, 0, 0)
keybd_event(VK_LWIN, 0, KEYEVENTF_KEYUP, 0)
End Sub

Private Declare Sub keybd_event Lib "user32" (ByVal bVk As Byte, ByVal bScan As Byte, _
ByVal dwFlags As Long, ByVal dwExtraInfo As Long)
Private Const KEYEVENTF_KEYUP = &H2
Private Const VK_LWIN = &H5B

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

End Class