You have initiated an active operating system fingerprinting attempt with nmap against a target system: What operating system is the target host running based on the open ports shown above?

Windows XP was released after Windows 2000 and has a distinct TCP/IP stack fingerprint with different TTL and window-size characteristics not matching the shown output.

Windows 98 SE uses an older TCP/IP stack without native SMB-over-445 support and lacks the RPC endpoint mapper port pattern seen on server editions.

Windows NT4 Server predates native SMB-over-port-445 and has a distinct TCP sequence number generation pattern that nmap distinguishes from Windows 2000.

Windows 2000 Server exposes a characteristic set of ports including 135 (RPC endpoint mapper), 139 (NetBIOS session), 445 (SMB over TCP), and 1025+ (dynamic RPC), which together form a fingerprint nmap's OS detection engine maps to Windows 2000 Server. Earlier Windows versions such as NT4 lack the native SMB-over-445 stack, and desktop editions such as XP and 98 SE do not present the same server-grade service combination or TCP/IP stack behavior.