Microsoft Knowledge Base Article 224829 contains the following summary:

This article describes the following TCP features in Microsoft Windows 2000 and Microsoft Windows Server 2003:

• TCP Window Size
• TCP Options Now Supported
• Windows Scaling - RFC 1323
• Timestamp - RFC 1323
• Protection against Wrapped Sequence Numbers (PAWS)
• Selective Acknowledgments (SACKS) - RFC 2018
• TCP Retransmission Behavior and Fast Retransmit
The TCP features can be changed by changing the entries in the registry.