Thanks to Michael Tsang Kwong Yiu for the tip: new hot-fix has been released for Windows NT 4.0 Service Pack 3, called landfix, that address the so-called "Land Attack." A Land Attack sends SYN packets with the same source and destination IP addresses and the same source and destination ports to a host computer. This makes it appear as if the host computer sent the packet to itself. Windows NT operates more slowly while the host computer tries to respond to itself.
You can find this fix on the Microsoft FTP site.
Also available is the "pent-fix" hot-fix, which fixes the latest Pentium bug that occurs when a specific set of invalid instructions is executed by the processor. This fix is also available on the Microsoft FTP site