Public Function GetCD(Datei As String) As String
Dim sDrives As String
Dim SplitDrive() As String
Dim N As Integer
Dim LaufwerksBuchstabe As String
  sDrives = GetAllDrives(DRIVE_CDROM)
  SplitDrive = Split(sDrives, ":")
  For N = 0 To UBound(SplitDrive) - 1
    If FileExists(SplitDrive(N) & ":\" & Datei) Then
      GetCD = SplitDrive(N)
      Exit For
    End If
  Next
End Function

 Private Function GetAllDrives(Optional ByVal DriveType As Long = 0) As String
  Dim I As Integer
  Dim Result As Long
  Dim Drives() As String
  Dim Dummy As String
  Dim sDrives As String
  Dummy = Space(255)
  Result = GetLogicalDriveStrings(Len(Dummy), Dummy)
  Drives = Split(Dummy, Chr$(0))
  For I = 0 To UBound(Drives) - 1
    If GetDriveType(Drives(I)) = DriveType Or _
      DriveType = 0 Then
      sDrives = sDrives & Left$(Drives(I), 2)
    End If
  Next I
  GetAllDrives = sDrives
End Function

Private Function FileExists(Filename$) As Boolean
    On Error Resume Next
        FileExists = (Dir$(Filename$) <> "Hallo ich bin da.")
        Exit Function
End Function