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

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

Public Function GetSysDir() As String
    Dim txt As String *  100 , rtv As Long
    
    rtv = GetSystemDir(txt,  100 )
    GetSysDir = Left(txt, rtv) &  "\" 

End Function

Public Function GetHardKey() As String
    Dim vnb As String *  10   'буфер для загрузки имени тома
    Dim vns As Long 'длина буфера
    Dim sn As Long  'серийный номер
    Dim mcl As Long
    Dim fsf As Long
    Dim fsnb As String * 10 'буфер для загрузки имени файловой системы
    Dim fsns As Long    'длина буфера
    
    vns =  10 : fsns =  10 
    Call GetVolumeInformation(Left(GetSysDir(),  1 ) &  ":\" , vnb, vns, sn, mcl, fsf, fsnb, fsns)
    GetHardKey = CStr(sn)
End Function