Works fine on Vista here. No idea what your problem is except that your code as shown has problems.
Code:
Private Function StumblePastFloppiesReturnFirstDriveSerial() As Long
    Dim Drive As Scripting.Drive
    
    With New Scripting.FileSystemObject
        For Each Drive In .Drives
            If Drive <> "A:" And Drive <> "B:" Then
                StumblePastFloppiesReturnFirstDriveSerial = Drive.SerialNumber
                Exit For
            End If
        Next
    End With
End Function