The default setting for the Winlogon key entry ShutdownWithoutLogon in Windows NT allows users with physical access to shut down a Windows NT system without logging in.
TCP/IP implementation in Microsoft Windows 95, Windows NT 4.0, and possibly others, allows remote attackers to reset connections by forcing a reset (RST) via a PSH ACK or other means, obtaining the target's last sequence number from the resulting packet, then spoofing a reset to the target.
The Windows NT RPC service allows remote attackers to conduct a denial of service using spoofed malformed RPC packets which generate an error message that is sent to the spoofed host, potentially setting up a loop, aka Snork.
The WINS server in Microsoft Windows NT 4.0 before SP4 allows remote attackers to cause a denial of service (process termination) via invalid UDP frames to port 137 (NETBIOS Name Service), as demonstrated via a flood of random packets.