Windows XP runs some applications up to 10% faster with the latest service pack installed, a research firm has found.

"We were pleasantly surprised to discover that Windows XP Service Pack 3 (v.3244) delivers a measurable performance boost to this aging desktop OS," wrote staff at exo.performance.network, in a blog post.

The researchers found that a PC loaded with Microsoft (NSDQ: MSFT)'s XP SP3 completed the OfficeBench test suite in less than 50 seconds. A similarly configured system running Windows XP with Service Pack 2 took more than 50 seconds to complete the test suite -- which measures how quickly a computer can perform common tasks in Microsoft Word, PowerPoint, and Excel.

"Since SP3 was supposed to be mostly a bug-fix/patch consolidation release ... the unexpected speed boost comes as a nice bonus," the researchers wrote.

They added that XP SP3's slick performance may lead some computer users to forgo Windows Vista. Exo.performance.network found that with the new service pack, XP is now two times faster than the newer Microsoft OS.

The tests were conducted late last year on a prerelease build of XP SP3. So it's possible the final version is even faster.

It's not all four-star reviews for the service pack, however.

Within hours of its general release last week, Windows XP SP3 began drawing hundreds of complaints from users who claim the update is wreaking havoc on their PCs.

The problems with XP SP3, according to posters on Microsoft's Windows XP message board, range from spontaneous reboots to outright system crashes.

"My external disks are having trouble starting up, which results in Windows not starting up," complained user Michael Faklis, in a post Wednesday. "After three attempts [to install XP SP3] with different configurations each time, System Restore was the only way to get me out of deep s**t," said Doug W.

Another user said the service pack prevented him from starting his computer. "I downloaded and installed Windows XP Service Pack 3 Network Installation Package for IT Professionals," wrote Paul. "Now I can't get the computer to boot."

Dozens of other posters reported similar problems.

It's not uncommon for major operating system updates to cause problems. Typically, the glitches are caused by conflicts with software, such as drivers, system files, or applications, already resident on the user's PC. Microsoft has yet to indicate whether it will issue an update to address some of the problems, though it has done so with previous updates.

Microsoft released Windows XP SP3 to broad distribution on Wednesday. It's available from Microsoft's automated Windows Update service or as a file that can be pulled from the Download Center on the company's Web site.

The service pack should offer a number of enhancements over the current version of the OS, which Microsoft is phasing out after June 30. It includes all updates issued since Windows XP Service Pack 2 was released in 2004 and some new elements.

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