How to download from links other than direct links in VB.NET?

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VB

WinForms

I am compiling a program in VB.NET which downloads a past-paper (for example) from www.xyz.com but it seems that I cannot download from the link which appears to be like this: " http://xyz.com/index.php/directory/download?location=A%20Level/Biology/Edexcel/2001%20Jun/2001%20June%20Module%202B.pdf " but when I try to download from a direct link such as " http://www.somewebsite.com/files/afile.file " it works. Here is my code, so please tell me what to correct! Any help is greatly appreciated ( btw I am a beginner in VB.NET, so I need exact answers with explanations please)

Public Class Form1
  Dim downloadsize As Long
  Dim Downloadedsize As Long
  Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim req As Net.HttpWebRequest
    Dim resp As Net.HttpWebResponse
    req = Net.HttpWebRequest.Create("http://xyz.com/index.php/directory/download?location=A Level/Chemistry/Edexcel/2012 Jan/6CH08_01_msc_20120209.pdf")
    req.AllowAutoRedirect = True
    resp = req.GetResponse
    req.Method = Net.WebRequestMethods.Http.Get
    downloadsize = resp.ContentLength
    ProgressBar1.Maximum = downloadsize
    BackgroundWorker1.RunWorkerAsync()
    Timer1.Start()
End Sub

  Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
    My.Computer.Network.DownloadFile("http://xyz.com/index.php/directory/download?location=A Level/Chemistry/Edexcel/2012 Jan/6CH08_01_msc_20120209.pdf", "D:\edexcellogo.pdf", "", "", False, 60000, True)
  End Sub

  Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
    Downloadedsize = My.Computer.FileSystem.GetFileInfo("D:\pp.doc").Length
    ProgressBar1.Value = Downloadedsize
  End Sub
End Class