Thank you! Tested OK like this:
@'
<?xml version="1.0" encoding="utf-8"?>
<!--?xml version="1.0"?-->
<Test.New.Setting>
<Settings>
<Setting
Id = "1"
Line1="true"
Line2="false"
Line3="blah">
</Setting>
</Settings>
</Test.New.Setting>
'@ | Set-Content ($XMLFile = "$env:temp\test.xml")
$OutXMLFile = "$env:temp\ResultTestXML"
$xml = New-Object -TypeName XML
$xml.Load($XMLfile)
$node=$xml.SelectSingleNode('//Setting[@Id="1"]')
$node.Attributes
$node.RemoveAttribute('Line2')
$node.Attributes
$xml.Save($OutXMLFile)
Get-Content $OutXMLFile
Remove-Item $OutXMLFile -Verbose