"Yes, Vista has a bad image, but still it's supported and falls within the product life cycle," added another commenter. "Not supporting Vista will send a BAD signal."
According to Web metrics company Net Applications, Windows 7 held a 24% share last month. Windows XP, with 54%, and Vista, with 11%, accounted for two-thirds of all operating systems.
Christian Kane, a researcher with Forrester Research who covers browsers, said Microsoft's move "made sense" because of Vista's poor showing and that OS's gradual decline in use.
Forrester's figures had Vista topping out at a 15% share of the enterprise market, and shrinking since then. "And most companies now see Vista as a stepping stone to Windows 7," Kane said.
Twenty percent of Forrester's corporate clients are now running Windows 7, he added.
"Microsoft wants to get everyone on Windows 7," said Kane, and excluding IE10 from other editions of Windows is part of that strategy. "This shows Microsoft's long-term commitment to Windows 7. I don't see it as shortsighted at all."
Other browser makers, most notably Firefox developer Mozilla, have blasted Microsoft for abandoning XP, saying that it's possible to tack on some support in the aged OS for hardware acceleration, the feature that Microsoft said drove it to ignore XP with IE9.
Google, whose Chrome also runs on both XP and Vista, did not reply to a request for comment today on Microsoft's IE10 decision. Mozilla declined to comment.
IE10's first preview weighs in at 19MB, and can be downloaded from Microsoft's Test Drive site.