The price is a break with tradition. In the run-up to both Vista in 2006 and , Microsoft and computer makers provided upgrades for either no cost or for a small fee. Details varied because the computer manufacturers, known as OEMs, delivered the upgrade.

Those deals were limited to corresponding editions: In other words, someone buying a PC running Windows Vista Home Premium could upgrade only to Windows 7 Home Premium.

This is the first time that Microsoft has offered a higher-level version to fulfill the upgrade.

Microsoft promised that it would publish more information Friday about the Windows 8 offer, presumably including details such as how users will obtain the upgrade and when.

The company also again said it would roll out additional promotions in the coming months, hinting that it will repeat the 2009 pre-sales event where it sold Windows 7 upgrades for as much as .