IE10 will run on Windows 8, Windows RT and Windows 7: Early on, Microsoft confirmed that the browser would not work on Windows Vista, much less Windows XP, which remains stuck on 2009's IE8.

Microsoft was the first, and so far, only, vendor to drop Vista from the support list of a new browser, just as it was the first -- and again, the only -- developer to abandon Windows XP.

Nearly a year ago, Microsoft pledged to ship beta and RC, or "release candidate," builds of IE10 for Windows 7. "We will release an IE10 Beta and Release Candidate on Windows 7 prior to IE10's general availability," said a commenter labeled as identified elsewhere as the in-house editor of the IE team's engineering blog.

Assuming that "general availability" meant the first public appearance of the browser, which will happen next week, that promise was never kept.

Instead, Microsoft will release what it calls a "preview" -- a relatively new term that has been applied equally to either beta or release candidate milestones -- about three weeks after IE10's debut on Windows 8.