Windows Vista users jumped at Microsoft's troubled operating system's first service pack, but people running Windows XP haven't been in much of a hurry to install its newest service pack update, a Windows performance and metrics researcher said Thursday.

According to Devil Mountain Software, by the end of July, 86% of the machines in its community-based Exo.performance.network (Xpnet) running Vista had been upgraded to Service Pack 1 (SP1).

That was a 17-point increase over the 69% who reported running Vista SP1 at the end of April, six weeks after Microsoft released the major update.

"There was pent-up demand for Vista SP1," said Craig Barth, chief technology officer at Devil Mountain. "If users are frustrated with a platform, they're going to be more likely to go out and snag any update that purports to fix the problems."

Meanwhile, Windows XP users have apparently felt less pressure to download and install that aged operating system's Service Pack 3 (SP3), which was released in early May.

The service-pack uptake difference between Vista and XP has been dramatic. Where more than two-thirds of the network's Vista users had grabbed SP1 within six weeks, fewer than half -- just 47% -- of XP users had updated to SP3 by the end of July, more than 12 weeks after Microsoft first posted it for download.

"Windows XP users were generally happy with Service Pack 2," Barth said. "There was not a huge clamor for [Windows XP] SP3 like there was for Vista SP1, and that shows in the results. It's pretty clear that a lot of XP users are very content with SP2."

The well-publicized troubles that some users had with XP SP3 -- including endless reboots after installing the service pack on PCs equipped with processors made by Advanced Micro Devices (AMD) -- may have had some impact on its uptake, Barth acknowledged.

But Microsoft's own emphasis may also have played a part. "Microsoft didn't promote XP SP3," he said. "They heavily promoted Vista SP1, and went out of their way to put a good foot forward for it. But they barely mentioned XP SP3."

Devil Mountain's Xpnet collects data from more than 3,000 PCs, 70% of which run Windows XP, Barth said. Users can join the network by downloading and installing a small utility, DMS Clarity Tracker Agent, from Devil Mountain's site.