add/remove printer

[] to add a new network printer

PS> (New-Object -ComObject WScript.Network).AddWindowsPrinterConnection("\\Printserver01\Xerox5")

[] to set the default printer

PS> (Get-WmiObject -ComputerName . -Class Win32_Printer -Filter "Name='HP LaserJet 5Si'").SetDefaultPrinter()

or,
PS> (New-Object -ComObject WScript.Network).SetDefaultPrinter('HP LaserJet 5Si')

[] to remove a printer connection

PS> (New-Object -ComObject WScript.Network).RemovePrinterConnection("\\Printserver01\Xerox5")