The window to upgrade to the next version of Microsoft's computer operating system is now open.
Microsoft began accepting orders for Windows 8 this week. The new operating system won't be delivered until October 26, however.
People who own a personal computer running earlier versions of Windows can buy the revamped system from $19.99.
The 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 a higher price if they want to upgrade.
The chance to upgrade at these prices expires January 31.
Microsoft designed Windows 8 so it can power both traditional PCs and tablet computers in response to the iPad's popularity.