Hi Morrish,
You need to fill the combobox using Dataset.
Here's how you could do it.
Dim conn As New SqlConnection(connString)
Dim strSQL As String = "SELECT * FROM Disk"
Dim da As New SqlDataAdapter(strSQL, conn)
Dim ds As New DataSet
da.Fill(ds, "Disk")
With ComboBox1
.DataSource = ds.Tables("Disk")
.DisplayMember = "Disk_Name"
.ValueMember = "Disk_Key"
.SelectedIndex = 0
End With