To create an instance of a com object
New-Object -comobject <ProgID>
$a = New-Object - comobject "wscript.network"
$a.username
To create an instance of a .Net Framework object. Parameters can be passed if required
New-Object -type <.Net Object>
$d = New-Object -Type System.DateTime 2006,12,25
$d.get_DayOfWeek()