VB问题，输出硬盘序列号

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 Sub Command1_Click()
Dim Driver, VolName, Fsys As String
Dim volNumber, MCM, FSF As Long
Driver = "c:\"
res = GetVolumeInformation(Driver, VolName, 127, volNumber, MCM, FSF, Fsys, 127)
Label9.Caption = volNumber
End Sub