Service Pack 2 for Windows XP, in addition to providing a host of security enhancements, will block pop-ups in Internet Explorer (IE) by default, Microsoft said Wednesday.

The beta version of the Windows XP update released in December last year always included a pop-up blocker, but the feature was turned off by default. Starting with the latest test version of Service Pack 2 (SP2), called Release Candidate 1 (RC1), pop-up blocking will be activated by default, according to an update to the fact sheet for Windows XP SP2 on Microsoft's Web site.

Microsoft made RC1 of Windows XP SP2 available to beta-testers on Wednesday and plans to make it more broadly available through a technical preview program on Friday. The company will take in feedback and is planning a Release Candidate 2 version before final release of the service pack during the first half of the year, said Greg Sullivan, lead product manager for Windows at Microsoft.

Windows XP SP2 is more than the usual roll-up of bug fixes and updates. It is also being used to make significant changes to the software that are designed to improve security. Changes to Windows XP made by SP2 fall into four main areas: network protection, memory protection, e-mail security and browsing security.

RC1 of Windows XP SP2 will be available publicly through a technical preview program. However, RC1 is still a test version and it is primarily meant for IT professionals so they can do compatibility and regression testing and give Microsoft feedback, Sullivan said.

"This is for a broader range of IT managers to get their hands on the SP2 bits and test it against their applications and give us any feedback they might have," Sullivan said. "It is still a prerelease version that we are not recommending the average consumer download."

Pop-up blocking is switched on because customers requested it, Sullivan said. Users will be able to decide which sites they want to see pop-ups from by adding those to a safe sites list. Pop-ups from Intranet sites and applications that use Internet Explorer's local intranet zone won't be blocked, so as not to interfere with corporate applications, Sullivan said.

Other features that are new in RC1 of Windows XP SP2 compared to the beta release include the Windows Security Center, a central place for Windows XP users to check important security settings, and access to a new version of the Windows Update service for security patches and other updates, Sullivan said.

The new Windows Update Service, version 5, offers a new interface that is designed to make it easier for users to decide which updates they want to download and install automatically, Sullivan said. Also, the service supports technology to make downloads smaller by only offering only relevant bits of code that need updating, Sullivan said.

The Windows XP SP2 RC1 technical preview program is expected to be online on Friday at http://www.microsoft.com/sp2preview/.