What is the BCD store?

The Boot Configuration Data (BCD) store contains boot configuration parameters and controls how the operating system is started in Microsoft® Windows Vista™ and Microsoft® Windows Server™ Code Name "Longhorn" operating systems. These parameters were previously in the Boot.ini file (in BIOS-based operating systems) or in the nonvolatile RAM (NVRAM) entries (in Extensible Firmware Interface–based operating systems). You can use the Bcdedit.exe command-line tool to affect the Windows® code which runs in the pre-operating system environment by adding, deleting, editing, and appending entries in the BCD store. Bcdedit.exe is located in the \Windows\System32 directory of the Windows Vista partition.

Why was there a change to BCD from Boot.ini?

BCD was created to provide an improved mechanism for describing boot configuration data. With the development of new firmware models (for example, the Extensible Firmware Interface (EFI)), an extensible and interoperable interface was required to abstract the underlying firmware. This new design provides the foundation for a variety of new features in Windows Vista (for example, the Startup Repair tool and Multi-User Install shortcuts).