Quickly Disable Network Cards using PowerShell

$Computer = "."
$net = Get-WMIObject -class Win32_NetworkAdapterConfiguration -ComputerName $computer
$netenabled = $net | where {$_.IPenabled}
foreach ($NetCard in $netenabled) {
    "Releasing lease on: {0}" -f $netcard.caption
	$netcard.ReleaseDHCPLease()
}