# Needed once
$Creds = Get-Credential
($Creds).Password|ConvertFrom-SecureString | set-content C:\temp\webfiles.txt

# Used everytime
$User = ""
$password = Get-Content C:\Temp\webfiles.txt | ConvertTo-SecureString
$credential = New-Object System.Management.Automation.PsCredential($User,$password)

# Magic
$Content = Invoke-WebRequest -Credential $credential http://strandbo.org/webfiles/simple.xml -AllowUnencryptedAuthentication