Private Declare Function GetVolumeInformation Lib "kernel32" Alias _
  "GetVolumeInformationA" (ByVal lpRootPathName As String, ByVal _
  lpVolumeNameBuffer As String, ByVal nVolumeNameSize As Long, _
  lpVolumeSerialNumber As Long, lpMaximumComponentLength As Long, _
  lpFileSystemFlags As Long, ByVal lpFileSystemNameBuffer As String, ByVal _
  nFileSystemNameSize As Long) As Long
Private Const MAX_FILENAME_LEN = 255
 
Public Function DiskSerial() As String
On Error GoTo FEHLER
    Dim RetVal As Long
    Dim str As String * MAX_FILENAME_LEN
    Dim str2 As String * MAX_FILENAME_LEN
    Dim a As Long
    Dim b As Long
    Call GetVolumeInformation("A:\", str, MAX_FILENAME_LEN, RetVal, a, b, str2, _
      MAX_FILENAME_LEN)
    DiskSerial = CStr(RetVal)
    Exit Function
FEHLER:
MsgBox Err.Description, vbExclamation
End Function