Do-it-yourself downgrades will be more complex with Windows 8, however, as users must first modify the PC's BIOS to boot into what's called "legacy mode." By default, Windows 8 will use UEFI-mode (Unified Extensible Firmware Interface) boot on new PCs to enable some new features, including Secure Boot.

Notebooks, desktops and other devices powered by Windows 8 Pro will go on sale Oct. 26.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at , on or subscribe to . His email address is .

See .

in Computerworld's Windows Topic Center.