Windows XP Service Pack 3 (SP3), will not make any noticeable cosmetic changes to your operating system, but it does offer several security improvements that are worth having. In addition, some claim it will slightly boost XP's speed as well.

Here are the main features of the upgrade to XP.

Security changes

Most of what's new has to do with security. In fact, five of the seven changes Microsoft lists on its release notes are security-related.

Particularly notable is network access protection (NAP), which is available on Vista and on Windows Server 2008, but until now was not available on XP. NAP gives network administrators a way to determine a computer's access to network resources based on the PC's identity, and whether the PC complies with security policies set by the administrator. With NAP, network administrators can set this kind of access at a finely granular level. In addition, NAP gives the administrator tools to bring the PC into compliance with the security policies, and then give the PC access to the network.

In addition, Microsoft has beefed up security by upgrading the random number generator. Last November, Israeli researchers said that attackers could exploit a weakness in Windows' pseudo-random number generator and be able to predict encryption keys. In SP3, Microsoft claims that flaw is fixed.

SP3 also rolls up a variety of previous patches and hot-fixes. Particularly noteworthy for Wi-Fi users is Wi-Fi Protected Access 2 (WPA2), which supports the new Wi-Fi Alliance certification for secure wireless networks. WPA2 is already available in Windows Vista and Windows Server 2003 with SP2.

A performance boost?

Microsoft did not claim any performance boosts for SP3, but one firm, after testing an earlier version of SP3, claims that in fact, users of Microsoft Office will see a moderate speed boost.

Using a previous version of SP3, Devil Mountain Software, ran its OfficeBench suite performance tests pre-SP3 and post-SP3 on an Office 2007-equipped notebook with a 2.0-GHz Intel Core 2 Duo processor and 1GB of memory. The company found a 10 percent speed increase compared to the pre-SP3 version of XP, which was equipped with XP SP2.

Craig Barth, Devil Mountain's chief technology officer, wrote in his company's blog, "Since SP3 was supposed to be mostly a bug-fix/patch consolidation release - unlike w/Vista SP1, Microsoft made no promises of improved performance for XP - the unexpected speed boost comes as a nice bonus."

On my test machine - the afore-mentioned laptop - I didn't notice a perceptible difference in performance between Microsoft Office 2007 pre-SP3 and post-SP3. But I'm not sure that a 10 percent difference would be noticeable.

The bottom line? If you're an IT pro and need to test out SP3 before its official launch, it's worth trying out now. Others might as well wait for the final version - there's nothing that's an absolute must-have right now, but the improved security will be worth it in the long run.