Option Explicit

Private Declare Function GetSystemDirectory Lib "kernel32" _
    Alias "GetSystemDirectoryA" (ByVal lpBuffer As String, _
    ByVal nSize As Long) As Long

Function GetSysDir() As String
  Dim strDir  As String
  Dim nLen    As Long

  strDir = Space(255)
  nLen = GetSystemDirectory(strDir, 255)
  strDir = Left(strDir, nLen)

  If Right$(strDir, 1) <> "\" Then strDir = strDir & "\"

  GetSysDir = strDir
End Function

MsgBox "Systemverzeichnis: " & GetSysDir