The Windows Boot Manager is capable of natively reading supported file systems, and it uses that capability to parse the BCD registry file without fully loading the file system. For computers that have a single operating system, Windows Boot Manager never displays a user interface. It does, however, wait for a few moments to allow the user to press a key to display the standard boot menu or to press F8 to choose Advanced Boot Options. If the user does not press a key within a few seconds of POST completing, Windows Boot Manager starts the Windows Boot Loader, which in turn starts Windows 7.

For computers with multiple operating systems installed (such as both Windows 7 and Windows XP), Windows Boot Manager displays a menu of operating system choices at startup. Depending on what you choose, Windows Boot Manager will start a different process:

• If you choose Windows Vista or Windows 7, Windows Boot Manager starts the Windows Boot Loader to open Windows.
• If you choose Earlier Version Of Windows or another entry for Windows Server 2003, Windows XP Professional, Microsoft Windows 2000, or Microsoft Windows NT 4.0, Windows Boot Manager starts Ntldr, which then proceeds with the hardware detection phase.
• If you select another operating system, control is passed to the boot sector for the other operating system.
• If you choose Windows Memory Diagnostic by pressing the Tab key, Windows Boot Manager starts the diagnostic tool without first opening Windows.