What is the different between xp serrvice pack 1 and 2

A service pack is a collection of all updates released to that point, and often includes new features, as well.

The major enhancements in Windows XP Service Pack 2 include Security Center, Automatic Updates, Windows Firewall, and Internet Explorer.

Security Center is an entirely new feature provided by Windows XP Service Pack 2. The Security Center service runs as a background process in Windows XP and routinely checks the status of the following components:
1. Windows Firewall: Security Center detects whether Windows Firewall is enabled or disabled. Security Center can also detect the presence of some third-party software firewall products.
2. Automatic Updates: Security Center detects the current Automatic Updates setting in Windows XP. If Automatic Updates is turned off or not set to the recommended settings, the Security Center provides appropriate recommendations.
3. Virus Protection: Security Center detects the presence of antivirus software from many third-party organizations. If the information is available, the Security Center service also determines whether the software is up-to-date and whether real-time scanning is turned on.

When Security Center detects an important security condition (such as improper settings), it displays a pop-up notice in the notification area.

Windows XP Service Pack 2 provides several enhancements to the Automatic Updates feature, including the following:
■ The latest version of Automatic Updates offers expanded support for Microsoft products, including Microsoft Office.
■ Previous versions of Automatic Updates could download only critical updates. Now Automatic Updates can download updates in the following categories: security updates, critical updates, update roll-ups, and service packs.
■ Automatic Updates now prioritizes the download of available updates based on the importance and size of the updates. For example, if a large service pack is being downloaded, and a smaller security update is released to address an exploit, that security update will be downloaded more quickly than the service pack.
■ Automatic Updates is now more automated. The need for users to accept End-User License Agreements (EULAs) has been eliminated. Also, the user now has a choice of whether to restart the computer following the installation of updates that might require a restart. Updates that do require a restart can now be consolidated into a single installation so that only one restart is required.

Previous versions of Windows XP include a software-based firewall named Internet Connection Firewall (ICF). After installing Windows XP Service Pack 2, this firewall is replaced by Windows Firewall.
Windows Firewall boasts a number of enhancements, including the following:
1. Windows Firewall is now enabled by default on all network
connections.
2. Windows Firewall provides an interface for configuring global settings that apply to all the connections of the computer.
3. In Windows XP Service Pack 2, Windows Firewall supports a new feature that allows you to keep Windows Firewall enabled and also not allow any exceptions; only solicited traffic is allowed. This new feature is intended to create an even more secure environment when connecting to the Internet in a public location or other unsecured location.
4. In Windows XP Service Pack 2, a startup Windows Firewall policy performs stateful packet filtering during startup, so that the computer can perform basic network tasks (such as contacting
DHCP and DNS servers) and still be protected.
5. In previous versions, you could not apply firewall rules based on Internet Protocol (IP) addresses. In Windows XP Service Pack 2, you can configure Windows Firewall so that firewall rules apply to IP addresses (or IP address ranges), meaning that only traffic from computers with valid IP addresses is allowed through the firewall.
6. In previous versions, you configure permitted traffic by specifying the TCP and UDP ports used by a service or application. In Windows XP Service Pack 2, you can also configure permitted traffic by specifying the file name of the application. When the application runs, Windows firewall monitors the ports on which the application listens and automatically adds them to the list of allowed incoming traffic.

Internet Explorer:
Windows XP Service Pack 2 introduces a number of new security features to Internet Explorer 6. As with the rest of the enhancements introduced with Windows XP Service Pack 2, most of the updates to Internet Explorer are intended to provide better security.

Well, if ya really gotta know, read all about it:
SP1: http://support.microsoft.com/kb/324722

SP2: http://support.microsoft.com/kb/811113

SP3: http://www.winsupersite.com/faq/xp_sp3.asp