That question is important: Last December, Microsoft announced it would automatically upgrade IE so that users ran the newest version suitable for their copy of Windows. Under the plan, Windows XP users still on IE6 or IE7 would be updated to IE8, while Windows Vista or Windows 7 users running IE7 or IE8 would be pushed to IE9.
Previously, Microsoft had always asked users for their permission before upgrading IE from one version to the next, even if Windows' automatic updates was enabled. If Microsoft applies that new practice to IE10 and Windows 7, it could automatically upgrade IE8 and IE9 on that OS to IE10 without informing users.
When asked whether the "silent upgrade" would apply to IE10 on Windows 7, and if so, whether it would do so at the launch of the new browser or at some later date, the Microsoft spokeswoman used the company's usual "no comment" phrasing of: "We have no information to share."
The absence of IE10 on Windows 7 makes moot analysts' predictions last year that Microsoft was moving toward an annual release cycle for the browser. They came to that conclusion after Microsoft announced IE10 just weeks after the March 2011 release of IE9.
"They don't want to be in the three- or even two-year cycle," Al Hilwa, an analyst with IDC, said in an interview at the time, referring to the 29 months between IE7 and IE8, and the 24 months between IE8 and IE9. "They got the memo on that. It doesn't work for browsers, or for any piece of software for that matter."
If Windows 8 ships in October, as most experts expect, the span between IE9 and IE10 would be approximately 19 months.
The desktop edition of IE10 will run only on Windows 7, Windows 8, Server 2008 R2 and Server 2012. Windows Vista, the 2007 operating system that never really caught on with users, cannot run IE10, and instead will be stuck at IE9, just as Windows XP can run no version newer than IE8.
Microsoft was the first browser maker to drop Vista from the support list of a new browser, just as it was the first -- and so far, only -- vendor to abandon Windows XP.
The company may not care about Vista: The 2007 OS powered just 7 percent of all Windows PCs that went online last month, according to Web metrics company Net Applications.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is firstname.lastname@example.org.
Read more about browsers in Computerworld's Browsers Topic Center.
This story, "Internet Explorer 10: MIA from Windows 7" was originally published by Computerworld.