try this:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
PlaySoundFile("startup.wav")
End Sub
Private Declare Function WCE_PlaySound Lib "CoreDll.dll" Alias "PlaySound" _
(ByVal szSound As String, ByVal hMod As IntPtr, ByVal flags As Integer) As Integer
Public Shared Sub PlaySoundFile(ByVal soundFile As String)
Const SND_ASYNC = &H1
Const SND_FILENAME = &H20000
WCE_PlaySound(soundFile, IntPtr.Zero, SND_ASYNC Or SND_FILENAME)
End Sub