Windows OS Installation Lifecycle.

Hey friends today Windows have gone too too far in every case but the roots remain the same. Today also most of the user's prefer to use Windows XP due to its simplicity. So I decided to give you all an overview of this product.Do leave a comment in any case if like or if you dont.
Windows XP comes in a number of versions, including a Home version and a Professional version.Windows XP Home is configured for home users. Windows XP Professional, which is configured to work as a workstation client, is a somewhat more powerful configuration for business users. Throughout this book, I’ll point out any differences in usage between the Home and Professional versions.

While not the focus of this book, Windows also comes in a number of server versions named Windows .NET. Microsoft has planned several server product offerings, including Windows .NET Server

and Windows .NET Advanced Server. We don’t expect that there will be major changes in .NET’s use of the registry.

In general everything remains same for Windows Vista (all Versions), Windows 7 (all Versions).The registry is a tree-based hierarchical system that offers quick access to data stored in almost any format. Actually, the registry is a rather flexible database. Registry information comes from a number of sources:

◆ From installing Windows

◆ From booting Windows

◆ From applications, systems, and user interaction

Every component of Windows uses the registry, without exception. A set of APIs allows both Windows and other applications to access registry information easily and quickly.Windows starts to use the registry at the very beginning stages of system boot up. The Windows boot process is based on which file format is installed, though the important parts are identical in either case. The unimportant parts are the loading of the specific drivers to read the

NTFS file system.

Note Throughout this book, I’m referring to Windows installed on an Intel x86 platform. There are differences in

the boot process on RISC-based systems (such as the Digital Alpha system), though these differences are not terribly significant,

considering how the registry is used. However, it seems that non-Intel systems are becoming very unusual, and they

probably will receive little or no support from Microsoft in the future.

The Windows boot process consists of the following steps:

1. The system is powered up, the video is initialized, and the 
    hardware self-tests are performed.The BIOS performs these tests,
    which are called POSTs(power-on self-tests). Usually, the memory
    test is the most visible one; its progress is shown on most
    computer screens.

2. After running POST, the system initializes each adapter. If the
    adapter has its own built-in BIOS, the adapter’s BIOS is called to
    perform its own initialization. For IDE adapters (most computers
    have either two or four IDE adapters), each connected drive
    (there may be up to two drives for each IDE adapter, allowing for
    a total maximum of eight IDE type drives) is queried for its
    specifications and access method.Some adapters, such as
    Adaptec’s SCSI adapters, display messages and allow the user to
    interact.Some adapters that don’t have a BIOS aren’t initialized
    until Windows loads their drivers much later in the boot-up
    process.

3. After all the adapters that have a BIOS have been initialized, the
    system boot loader reads in

    the sector located at the very beginning of the first bootable disk
    drive and passes commands

    to this code. This sector is called the boot sector, or the MBR
    (Master Boot Record), and it is written by the operating system
    When the operating system is installed.

4. The code in the MBR then loads the NTLDR file. (This file has
     no extension, though it is an executable file.) Once loaded, the
     MBR passes control to the code in NTLDR.

5. NTLDR then switches into 32-bit mode. (Remember, an Intel x86
    processor always boots into 16-bit real mode.) It then loads a
    special copy of the necessary file system I/O files and reads in the
    file boot.ini.

6. The file boot.ini has information about each operating system that
    can be loaded. Remember,Windows supports multiboot
    configurations. It is trivial to create a Windows installation that
    can boot Windows NT, Windows, and Windows 95 or
    Windows98. The boot loader can even boot two different copies
     of Windows with either the same or different version numbers.
     NTLDR then processes boot.ini, displaying boot information that
     allows the user to select which operating system will be loaded.
     At this point, let’s assume that Windows will be loaded.

7. When you select Windows to be loaded, NTLDR loads the file
    ntdetect.com. This program then collects information about the
    currently installed hardware and saves this information for the
    registry. Most of this information is stored in the
    HKEY_LOCAL_MACHINE hive.

8. Once NTDETECT has detected the hardware, control is passed
    back to NTLDR, and the boot process continues. At this point,
    the registry has been substantially updated with the current

    hardware configuration, which is stored in
    HKEY_LOCAL_MACHINE\Hardware.

9. The prompt to select the configuration is then presented. This
     prompt, “Press spacer now to invoke Hardware Profile/Last
     Known Good menu,” allows you to force Windows to use a
     specific configuration as stored in the registry hive
     HKEY_LOCAL_MACHINE.

10. Following the detection of NTDETECT, NTLDR loads and
      initializes the Windows NT kernel, loads the services, and then
      starts Windows.

11. When the kernel is loaded, the HAL is also loaded. 
      (The HAL—Hardware Abstraction Layer—is used to manage
      hardware services.) Next, the registry system sub-key
      HKEY_LOCAL_MACHINE\System is loaded into memory.
      Windows scans the registry for all drivers with a start value of

      zero. This includes those drivers that should be loaded and
      initialized at boot time.

12. You can see the beginning of the next stage, kernel initialization.
      The screen switches to a blue background, and you see a
      message about the Windows build number and the number of

      system processors. Again, the system scans the registry and finds
      all drivers that must be started at the kernel initialization stage.

13. From this point, Windows starts various components and
      systems. Each component and system reads the registry and
      performs various tasks and functions. In the final stage, the
      program that manages the user logon, WinLogon, starts.
      WinLogon allows the user to log on and use Windows.

Once Windows is booted, both the operating system and applications use the registry. The registry is dynamic, but usage of the registry may be dynamic or static. That is, some registry items

are read one time and never reread until the system is restarted. Other items are read every time they are referenced. There is no fixed rule as to what is read each time it is needed and what is not, but to be on the safe side, follow these guidelines:

◆ Application-related data is probably read when the application
     starts. If you change application-based data, restart the
     application. In fact, the best path to follow is this: do not change

     application-based data while the application is running.

◆ User-interface data is sometimes dynamic, sometimes static. With
     user-interface data, the way to go is to change the data and wait
     to see the results of the change. If the change doesn’t appear, try
     logging on again.

◆ System data is usually either static or otherwise buffered. Many
     system-related registry changes won’t become effective until the
     system is restarted. Some system data is rewritten, or created, at

     startup time, precluding changes by users. Many of the items in
     HKEY_LOCAL_MACHINE may be reset at system boot time,
     especially those items that are hardware related