Reading GUID

Does anyone know a simple way for a VB6 Active X EXE to read a unique identifier from a machine (particularly the HDD GUID) for anti-piracy. I gues one could do it using the registry but it would be much better if there is a more robust way that does not involve downloading an extra DLL just for the purpose.

Retrieving a disk's serial number
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Add this code to a new module:
Declare Function GetVolumeInformation _
Lib "kernel32.dll" _
Alias "GetVolumeInformationA" _
(ByVal lpRootPathName As String, _
ByVal lpVolumeNameBuffer As String, _
ByVal nVolumeNameSize As Integer, _
lpVolumeSerialNumber As Long, _
lpMaximumComponentLength As Long, _
lpFileSystemFlags As Long, _
ByVal lpFileSystemNameBuffer As String, _
ByVal nFileSystemNameSize As Long _
) As Long

Function GetSerialNumber(sDrive As String) As Long
Dim lSerial As Long
Dim lRetVal As Long
Dim sTempA As String
Dim sTempB As String
sTempA = String$(255, Chr$(0))
sTempB = String$(255, Chr$(0))
lRetVal = GetVolumeInformation(sDrive, sTempA, Len(sTempA), lSerial, 0, 0, sTempB, Len(sTempB))
GetSerialNumber = lSerial
End Function

The GetVolumeInformation function also allows you to get other information about a disk, not only it's serial number, but most of the other parts are normally unused (unless you're a real power user)
To use this function, simply call when necessary:
Dim lSerialNum as Long
...
Private Sub Form_Load()
lSerialNum = GetSerialNumber("C:\")

' Do something with the serial number, for example check that
' this computer is authorised to use the program
End Sub