Your system may require one or more security patches or hotfixes from Microsoft.
The implementation of the Remote Data Protocol (RDP) in the terminal service in Windows NT 4.0 and Windows 2000 does not correctly handle a particular series of data packets. If such a series of packets were received by an affected server, it would cause the server to fail. The server could be put back into normal service by rebooting it, but any work in progress at the time of the attack would be lost. It would not be necessary for an attacker to be able to start a session with an affected server in order to exploit this vulnerability, the only prerequisite would be the need to be able to send the correct series of packets to the RDP port on the server.