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Windows Legacy OS Loader (NTLDR)

The normal startup sequence for Windows 7 is:

1. 2. 3. 4. 5. 6.

Power-on self test (POST) phase . Initial startup phase . Windows Boot Manager phase . Windows Boot Loader phase . Kernel loading phase . Logon phase .

This sequence will vary if the computer is resuming from hibernation or if a non Windows 7 option is selected during the Windows Boot Manager phase . The following sections describe the phases of a normal startup process in more detail .

As soon as you turn on a computer, its processor begins to carry out the programming instructions contained in the BIOS or EFI . The BIOS and EFI, which are types of firmware, contain the processor-dependent code that starts the computer regardless of the operating system installed . The first set of startup instructions is the POST, which is responsible for the following system and diagnostic functions:

Performs initial hardware checks, such as determining the amount of memory present Verifies that the devices needed to start an operating system, such as a hard disk, are present Retrieves system configuration settings from nonvolatile memory, which is located on the motherboard

The contents of the nonvolatile memory remain even after you shut down the computer . Examples of hardware settings stored in the nonvolatile memory include device boot order and Plug and Play (PnP) information . After the motherboard POST completes, add-on adapters that have their own firmware (for example, video and hard drive controllers) carry out internal diagnostic tests . If startup fails before or during POST, your computer is experiencing a hardware failure . Generally, the BIOS or EFI displays an error message that indicates the nature of the problem . If video is not functioning correctly, the BIOS or EFI usually indicates the nature of the failure with a series of beeps . To access and change system and peripheral firmware settings, consult the system documentation provided by the manufacturer . For more information, refer to your computer s documentation and see the section titled How to Diagnose Hardware Problems later in this chapter .

After the POST, computers must find and load the Windows Boot Manager . Older BIOS computers and newer EFI computers do this slightly differently, as the following sections describe .

After the POST, the settings that are stored in the nonvolatile memory, such as boot order, determine the devices that the computer can use to start an operating system . In addition to floppy disks or hard disks attached to Advanced Technology Attachment (ATA), Serial ATA, and small computer system interface (SCSI) controllers, computers can typically start an operating system from other devices, such as the following:

CDs or DVDs Network adapters Universal serial bus (USB) flash drives Removable disks Secondary storage devices installed in docking stations for portable computers

It is possible to specify a custom boot order, such as CDROM, Floppy, Hard Disk . When you specify CDROM, Floppy, Hard Disk as a boot order, the following events occur at startup:

The computer searches the CD-ROM for bootable media . If a bootable CD or DVD is present, the computer uses the media as the startup device . Otherwise, the computer searches the next device in the boot order . You cannot use a non-bootable CD or DVD to start your system . The presence of a non-bootable CD or DVD in the CD-ROM drive can add to the time the system requires to start . If you do not intend to start the computer from CD, remove all CDs from the CD-ROM drive before restarting . The computer searches the floppy disk for bootable media . If a bootable floppy is present, the computer uses the floppy disk as the startup device and loads the first sector (sector 0, the floppy disk boot sector) into memory . Otherwise, the computer searches the next device in the boot order or displays an error message . The computer uses the hard disk as the startup device . The computer typically uses the hard disk as the startup device only when the CD-ROM drive and the floppy disk drive are empty .

There are exceptions in which code on bootable media transfers control to the hard disk . For example, when you start your system by using the bootable Windows DVD, Windows Setup checks the hard disk for Windows installations . If one is found, you have the option of bypassing DVD startup by not responding to the Press Any Key To Boot From CD Or DVD prompt that appears . This prompt is actually displayed by the startup program located on the Windows DVD, not by your computer s hardware . If startup fails during the initial startup phase, you are experiencing a problem with the BIOS configuration, the disk subsystem, or the file system . The following error message is