As the slide shows, Microsoft is seeing adoption of 64-bit versions of its operating system rise steadily to more than 20 percent of new Windows Vista systems last month. "Internationally, we see the data is about half of this," DeVaan said.

The transition from 32- to 64-bits promises improved PC performance. Microsoft offers a fairly succinct explanation on its Windows Help site:

"The terms 32-bit and 64-bit refer to the way a computer's processor (also called a CPU), handles information.

"The 64-bit versions of Windows can utilize more memory than 32-bit versions of Windows. This helps minimize the time spent swapping processes in and out of memory by storing more of those processes in random access memory (RAM) rather than on the hard disk. This, in turn, can increase overall program performance."

Of course, as with any major computing transition, software and hardware makers have to get on board. More from the help site:

"To run a 64-bit version of Windows, your computer must have a 64-bit processor. To take advantage of the additional capability to utilize memory on 64-bit versions of Windows Vista, you should have at least 4 GB of RAM installed on your computer.

"Additionally, you will need to make sure that you have 64-bit drivers for your hardware and that your programs will run in a 64-bit Windows environment. Device drivers that are 32-bit do not work on computers running 64-bit versions of Windows."

DeVaan offered an interesting explanation for the increase in adoption. 64-bit machines can use more than 4 gigs of RAM and memory prices are coming down.

"Another dynamic that we see in the United States is that the retail channel is looking to use RAM upgrades as a way to boost margin," he said. "What that means is that 64-bit machine's run rate is increasing rapidly and that means our ability to support those 64-bit machines fully in the broad ecosystem is a really important thing."

Some background: At WinHEC in 2005, Bill Gates ushered in the 64-bit era, announcing versions of Windows XP Professional and Windows Server 2003. The shift from 16-bit to 32-bit was made with Windows 95.

The rate of 64-bit adoption is slower than what Microsoft originally forecast. In 2005, Microsoft expected about half of new PCs to come with 64-bit processors by the end of that year, and nearly all systems to be 64-bit within two years.