REDMOND, Wash. (AP) - The window to upgrade to the next version of Microsoft's computer operating system is now open.

Microsoft Corp. began accepting orders for Windows 8 this week. The new operating system won't be delivered until Oct. 26, however.

People who own a personal computer running earlier versions of Windows can buy the revamped system for $14.99 to $39.99.

The lower price is being offered to PC owners who have bought a machine powered by Windows 7 since June 2. Everyone else with a Windows-based computer will have to pay the higher price if they want to upgrade.

The chance to upgrade at these prices expires Jan. 31.

Microsoft designed Windows 8 so it can power both traditional PCs and tablet computers in response to the iPad's popularity.