Use this class:

Imports System.Diagnostics

Public Class Win32Windows

   Private Declare Function EnumWindows Lib "user32" (ByVal lpEnumFunc As
EnumWindowsDelegate, _
       ByVal lParam As Integer) As Integer
   Private Delegate Function EnumWindowsDelegate(ByVal Handle As IntPtr,
ByVal iParam As Integer) As Boolean
   Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal
hWnd As Integer, _
                   ByRef lpdwProcessId As Integer) As Integer

   Public Sub New(ByVal ProcessID As Integer)
       EnumWindows(AddressOf EnumWindowProc, ProcessID)
   End Sub

   Private ReadOnly m_oWindowList As New ArrayList

   Private Function EnumWindowProc(ByVal Handle As IntPtr, ByVal iParam As
Integer) As Boolean
       Dim hWnd As Integer = Handle.ToInt32()
       Dim iProcessID As Integer
       Dim iThreadID As Integer = GetWindowThreadProcessId(hWnd,
iProcessID)

       If iProcessID = iParam Then
           m_oWindowList.Add(Handle.ToInt32())
       End If

       Return True
   End Function

   Public ReadOnly Property WindowList() As IList
       Get
           Return m_oWindowList
       End Get
   End Property
End Class

Example:
       Dim list As New Win32Windows(Process.GetCurrentProcess().Id)
       For Each iHandle As Integer In list.WindowList
           Console.WriteLine(iHandle.ToString())
       Next

Hope this helps!

Shariq Khan
shariq@shariqkhan.com