System.Net.Webclient only download 81.4 MB (85,363,075 bytes)

[string] $fileName = "en_sql_server_2008_r2_developer_x86_x64_ia64_dvd_522665.iso"
[string] $url = "http://installers.abc/iso/$filename"
[string] $tempPath = "c:\balpreet"

function Download-Iso {
  Param(
    [string] $FileName,
    [string] $Url,
    [string] $destinationFolder 
  )

  [string] $destination = Join-Path -Path $tempPath -ChildPath $fileName 
  write-host "downloading from : $url to $destination"
    $client = new-object System.Net.WebClient
    $client.DownloadFile( $Url, $destination )

}

Download-Iso -FileName $fileName -Url $url -DestinationFolder = $tempPath

I'm trying to download 4.07 GB (4,380,329,984 bytes) ISO from remote location accessible over http.

Windows 7 : It download complete 4.07 GB file.

Windows Server 2008 R2 : It download only 81.4 MB (85,363,075 bytes) and pretend to completed the download. Code is not throwing any error, but not downloading complete file as well.

Any clue why?