Try 
       Dim dialog As New SaveFileDialog With { _
           .Filter = "Exe Files|*.exe" _
       }
       dialog.ShowDialog
       Dim num As Double = Conversion.Val(Me.NumericUpDown1.Value)
       File.Copy(Me.NsTextBox5.Text, dialog.FileName)
       If Me.NsRadioButton2.Checked Then
           num = (num * 1024)
       End If
       If Me.NsRadioButton1.Checked Then
           num = (num * 1048576)
       End If
       Dim stream As FileStream = File.OpenWrite(dialog.FileName)
       Dim i As Long = stream.Seek(0, SeekOrigin.End)
       Do While (i < num)
           stream.WriteByte(0)
           i = (i + 1)
       Loop
       stream.Close
       Interaction.MsgBox("Le fichier a bien " & ChrW(233) & "t" & ChrW(233) & " pumper", MsgBoxStyle.OkOnly, Nothing)
   Catch exception1 As Exception
       ProjectData.SetProjectError(exception1)
       Dim exception As Exception = exception1
       Interaction.MsgBox("Bug, merci de me prevenir sur Skype : Sofaws.off", MsgBoxStyle.OkOnly, Nothing)
       ProjectData.ClearProjectError
   End Try