Perhaps the easiest way to do it is like this:
Dim path1 As String = "D:\Music\Rock\Scorpions"
Dim path2 As String = "D:\Music\Rock\Scorpions\World Wide Live"
Dim topLeve11 As String = path1.Split("\"c)(1)
MessageBox.Show(topLeve11) 'Music
Dim topLeve12 As String = path2.Split("\"c)(1)
MessageBox.Show(topLeve12) 'Music
This splits the path using the '\' as the separator and then selects the second string in the resulting array, which has an index of 1.