Visual Basic - API para liberar memoria

Deseo saber el nombre de una Api para liberar memoria , puesto que cuando ejecuto una aplicación de Visual Basic a las tres o cuatro horas de su ejecucion da un error y no se puede abrir ningun archivo.Esta aplicación abre muchas ventanas de MS-DOS.

Gracias.

SIENTO QUE ESTE EN INGLES PERO CREO QUE ESTO ES LO QUE BUSCAS
Frees a block of task memory previously allocated through a call to the CoTaskMemAlloc or CoTaskMemRealloc function.
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Type BrowseInfo
hWndOwner As Long
pIDLRoot As Long
pszDisplayName As Long
lpszTitle As Long
ulFlags As Long
lpfnCallback As Long
lParam As Long
iImage As Long
End Type
Const BIF_RETURNONLYFSDIRS = 1
Const MAX_PATH = 260
Private Declare Sub CoTaskMemFree Lib "ole32.dll" (ByVal hMem As Long)
Private Declare Function lstrcat Lib "kernel32" Alias "lstrcatA" (ByVal lpString1 As String, ByVal lpString2 As String) As Long
Private Declare Function SHBrowseForFolder Lib "shell32" (lpbi As BrowseInfo) As Long
Private Declare Function SHGetPathFromIDList Lib "shell32" (ByVal pidList As Long, ByVal lpBuffer As String) As Long
Private Sub Form_Load()
'KPD-Team 1998
'URL: http://www.allapi.net/
'KPDTeam@Allapi.net
Dim iNull As Integer, lpIDList As Long, lResult As Long
Dim sPath As String, udtBI As BrowseInfo

With udtBI
'Set the owner window
.hWndOwner = Me.hWnd
'lstrcat appends the two strings and returns the memory address
.lpszTitle = lstrcat("C:\", "")
'Return only if the user selected a directory
.ulFlags = BIF_RETURNONLYFSDIRS
End With

'Show th