NEWT uses Windows APIs for scanning, so all remote administration ports should be opened. These include ports 135 through 139 (NetBIOS ports) and 445 (RPC/WMI). Also, if the firewall blocks ICMP Echo request by default, you\'ll want to open this as well.
If this is a one time push and you\'re not able to edit the settings afterwards, you may first want to test it on a few machines.
Please let us know if you have a problem.