"We are currently in the planning stages for Windows 7 and development is scoped to three years from Windows Vista consumer" general availability, a Microsoft spokesman said in an e-mail Friday to InformationWeek.
Windows Vista was released to consumers in late January 2007. That means Windows 7 would not be released until January 2010, according to Microsoft's statement.
Speaking at a seminar on corporate philanthropy last week in Miami, Gates said his company might ship a new version of its Windows operating system as soon as 2009.
The news agency Reuters quoted Gates as saying that Windows 7 may be released "sometime in the next year or so." That would put the software ahead of the three-year cycle that Microsoft normally works on for OS releases.
Microsoft said Gates may have been referring to trial versions of Windows 7. "As is standard with the release of a new product, we will be releasing early builds of Windows 7 prior to its general availability as a means to gain tester feedback," the spokesman said.
"We're not sharing additional information at this time," the spokesman added.
Microsoft to date has said little about Windows 7, which had been in development under the code name Blackcomb. It was generally believed that the OS would ship in the 2010 time frame.
Some computer users are hoping Windows 7 will present a slimmer profile than Vista.
To experience all of Vista's features, PC users need a computer with at least a 1-GHz processor, 1 GB of memory, and a 40-GB hard drive. By contrast, Windows XP Professional requires only a 300-MHz processor, 128 Mbytes of RAM, and a 1.5 GB disk.
Microsoft has extended the life of the older Windows XP OS for longer than originally planned -- in part to keep Linux out of the PC market's low end.
The company said last week that it would allow computer makers to continue to sell Windows XP on "ultra low-cost PCs", or ULCPCs, for an extended period.
Microsoft said it would allow system vendors to preload the Home edition of Windows XP on ULCPCs through June 2010, or one year after the next version of Windows becomes generally available.
Microsoft defines ULCPCs as, among other things, systems that use discount-line processors and lack a separate graphics card. Such low-spec machines would be incapable of running Vista.