PowerShell, Web Requests, and Proxies

Untested:

$user = $env:username
$webproxy = (get-itemproperty 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings').ProxyServer
$pwd = Read-Host "Password?" -assecurestring

$proxy = new-object System.Net.WebProxy
$proxy.Address = $webproxy
$account = new-object System.Net.NetworkCredential($user,[Runtime.InteropServices.Marshal]::PtrToStringAuto([Runtime.InteropServices.Marshal]::SecureStringToBSTR($pwd)), "")
$proxy.credentials = $account

$url = "http://stackoverflow.com"
$wc = new-object system.net.WebClient
$wc.proxy = $proxy
$webpage = $wc.DownloadData($url)
$string = [System.Text.Encoding]::ASCII.GetString($webpage)

...

Somewhat better is the following, which handles auto-detected proxies as well:

$proxy = [System.Net.WebRequest]::GetSystemWebProxy()
$proxy.Credentials = [System.Net.CredentialCache]::DefaultCredentials

$wc = new-object system.net.WebClient
$wc.proxy = $proxy
$webpage = $wc.DownloadData($url)

(edit) Further to the above, this definition appears to work fine for me, too:

function Get-Webclient {
    $wc = New-Object Net.WebClient
    $wc.UseDefaultCredentials = $true
    $wc.Proxy.Credentials = $wc.Credentials
    $wc
}