What are the various features offered by Windows Service Pack1?

Security Configuration Wizard: A tool that allows users ease to research, and make changes to, security policies.
Hot Patching: This feature is set to extend Windows Server 2003’s ability to take DLL, Driver, and non-kernel patches without a reboot.
IIS 6.0 Metabase Auditing: Allowing the tracking of metabase edits

Windows Firewall:It is more secure to the threats.It provides user to manage the incoming ports.

Other networking improvements include support for Wireless Provisioning Services, better IPv6 support, and new protections against SYN flood TCP attacks.
Post-Setup Security Updates: A default mode that is turned on when a Service Pack 1 server is first booted up after installation. It configures the firewall to block all incoming connections, and directs the user to install updates.

Data Execution Prevention (DEP): Support for the No Execute (NX) bit which helps to prevent buffer overflow exploits that are often the attack vector of Windows Server exploits.

Windows Media Player version 10.
Internet Explorer 6 SV1.