Late last week, Microsoft published data from market researchers showing that nearly half of all Windows 7 PCs worldwide are running a 64-bit version of the OS. That's a dramatic increase from previous Windows versions: Only 11 percent of the Windows Vista installed base—and less than 1 percent of Windows XP—is 64-bit.

"As of June 2010, we see that 46 percent of all PCs worldwide running Windows 7 are running a 64-bit edition of Windows 7," a post to the Windows team blog reads. "That is, nearly half of all PCs running Windows 7 are running 64-bit."

Microsoft has already moved its server OSs to 64-bit, and it's widely thought that with Windows 8—the next client version of Windows due in two years—the software giant might finally jettison 32-bit code for good on the PC desktop, as well. Still, 64-bit versions of Windows on the desktop offer few meaningful advantages over 32-bit versions, aside from support for dramatically more memory. Whereas 32-bit systems can utilize up to 4GB of RAM (actually a bit less in Windows), 64-bit systems can utilize a lot more. For example, Windows 7 Professional and higher can address up to 192GB of RAM.

What's most interesting about the 64-bit data Microsoft provided, perhaps, is that most new PCs sold today include 64-bit versions of Windows 7. In fact, almost 80 percent of Windows-based PCs sold at retail utilize a 64-bit version of the OS. (The rest are likely netbooks, which require a 32-bit version.) Because fewer than half of all Windows 7 installs worldwide are on 64-bit versions, however, this suggests that many people have upgraded from 32-bit versions of Vista or are still unfamiliar with 64-bit versions or worried about compatibility. (Microsoft provides both 32-bit and 64-bit versions of Windows 7 in its retail versions of the OS.)

That said, the hardware-compatibility problems that used to dog 64-bit versions of Windows are no longer applicable. "Hardware partners are required to develop 64-bit drivers for their devices, and software partners are required to have their applications compatible with 64-bit Windows 7," the blog post notes.