People are beginning to use 64-bit Windows Vista on PCs in favor of the 32-bit version of the OS faster than they have previously, Microsoft said this week.

However, analysts warn the uptick may have less to do with customers' interest in a 64-bit OS and more to do with the fact that so few people have, until now, used a 64-bit client version of Windows.

A post by a member of the Vista team, Chris Flores, on the Windows Vista Team Blog claims that the installed base of 64-bit Windows Vista PCs as a percentage of all Vista systems has more than tripled in the US in the past three months. He also wrote that worldwide adoption has more than doubled in the same time frame.

"Put more simply, usage of 64-bit Windows Vista is growing much more rapidly than 32-bit," Flores wrote, speeding up from the previously "glacial" movement toward the platform, driven mostly by "technology enthusiasts."

"Based on current trends, this growth will accelerate as the retail channel shifts to supplying a rapidly increasing assortment of 64-bit desktops and laptops," he wrote.

But don't be fooled by the numbers and think there is rampant interest among PC customers in 64-bit Vista, warned one analyst, who said that prior to Vista, use of 64-bit versions of the Windows client OS was virtually nil. "If you start from almost zero it's easy to triple," said IDC analyst Al Gillen.

He said that true adoption of 64-bit Vista -- or any Windows client OS for that matter -- is still a couple of years out. "Two things have to happen: people have to begin deploying Vista in a broad way, and have to believe that all of their applications are fully compatible with a 64-bit environment," Gillen said.

As for the latter, the inclusion of more peripheral drivers that are compatible with a 64-bit OS in Windows Vista Service Pack 1, released in April, may be responsible for the recent increase in 64-bit Vista users, said Mike Cherry, an analyst with Directions on Microsoft.

This adoption may continue to grow as PC makers are more comfortable putting a 64-bit version of Vista on PCs and selling them to customers now that they know third-party devices will be compatible with the OS, he added. But he still doesn't see people necessarily being "thrilled" by the idea of using 64-bit Vista.

"It's nice to see [64-bit use] tracking this way," Cherry said, then joked, "but I'm not going home to the wife and saying it's finally the time -- I have to go out and buy a 64-bit Windows [PC]. I just don't think people are excited by this kind of thing the way they used to be."

He also noted that because 64-bit Windows has not had widespread adoption, "low expectations" for its use could also explain why a tripling in numbers is a big deal to Microsoft.

Flores cited better overall performance and better responsiveness when many applications are running at once as the benefit of 64-bit PCs running 64-bit editions of Vista, which typically have 4 gigabytes (GB) of memory or more. In contrast, 32-bit systems top out at about 3GB of memory, which limits their performance, he said.

However, while a 64-bit OS means better PC performance, it wouldn't really be noticeable to the "average office worker" who only uses a PC for e-mail, the Internet and worker productivity applications, IDC's Gillen said.

"64-bit has some definite benefits, but it's about what kind of workloads you are pushing through your PC," he said.