What happens this week?
Microsoft plans promotional events in several cities Wednesday, tied to a global ad campaign and a series of charitable donations. About 5 million people who enrolled in an earlier test program will be able to download Windows 10 right away.
The company is also offering Windows 10 as a free download, any time over the next year, to anyone who has the Home or Pro versions of Windows 7 or 8 (but not the Enterprise versions used by big organizations). Some may not get it the first day; Microsoft says it will deliver downloads in waves, to ensure things go smoothly, but it hasn't said how long that will take. Details on how to upgrade are here: http://bit.ly/1eNCySl .
Retailers such as Best Buy, Staples and Wal-Mart will have some desktops and laptops with Windows 10 already installed. More models are coming.