A: In Windows 8 computers, a feature enabled by UEFI--Secure Boot--was designed to keep certain OSs and software from loading during startup. Secure Boot provides a secure handoff between the hardware and the desired OS, ensuring other code, such as malware, can't get in between the hardware and the signed OS or impersonate the OS.
Related: Windows 8 Dual Boot Video
When Secure Boot is used, there are often questions if dual-boot can still be used, allowing multiple OSs to boot on a single piece of hardware. Below is a summary of the dual-boot scenarios that can work:
- Windows 8 and another Windows 8 installation
- Windows 8 and a Windows 8 Windows To Go (for USB)
- Windows 8 and certain Linux distributions that have their loader signed and that are trusted by the hardware
Windows 8 and Windows 7 won't work, as the Windows 7 UEFI implementation requires a compatibility mode to be used, which does not work with Secure Boot.