Apparently, Windows Vista and Windows XP users will be out of luck. The latter came as no surprise, since the 11-year-old operating system is due for retirement in April 2014.

"The new Office is available as the traditional suite of client applications and as an always up-to-date subscription service called Office 365 Home Premium," said Microsoft in a supporting document. "Today, consumers can try the new Office by signing up for the Office 365 Home Premium Preview."

At release, Baller said that Office would also be available in the traditional disc-based packaging for local-only installation and operation where customers pay a one-time licensing fee.

Microsoft did not reveal prices for the new Office -- that, the company said, would come "later this fall" when it nears the launch date -- or define an on-sale window. Most analysts, however, have pegged the latter at early next year. If Microsoft follows the same development pace it used three years ago for Office 2010, the new Office will reach retail and most customers the last week of January 2013 or the first week of February.

When Office 365 Home Premium officially launches, it will include an additional 20GB of SkyDrive storage space and 60 minutes of Skype credit each month. Also included: Future upgrades, which will be free to subscribers.