Try this, see if it works faster:
 Code:
$WSHNetwork = CreateObject("WScript.Network")
$WSHPrinters = $WSHNetwork.EnumPrinterConnections
For $i=0 To WSHPrinters.Count -1
  If Left($WSHPrinters.Item($i),2) = "\\"
    $WSHNetwork.RemovePrinterConnection($WSHPrinter.Items($i),1,1)
  EndIf
Next