Windows Setup

Windows Setup is the installation process used to install Windows. Setup first prepares the system's hard drive for installation and then copies system files, programs, services, and drivers to the root of the installation drive allowing Windows to boot from the hard disk. After Windows is started for the first time, devices are set up, components are registered, and users set up their accounts.

Windows 1.0 and Windows 2.x
Windows 1.0 featured a very rudimentary setup application. The installer asks for the target drive, directory and hardware configuration, and then proceeds to install the operating system. There is no option to load custom drivers from the setup, with the user instead having to copy the drivers on the disk manually. In order to optimize performance, the installer also combines crucial system files into a single  file using what is called "Fast Boot". There is no support for changing a single part of the system, as the entire environment has to be clean installed in order to do that, erasing any configuration in the process.

Unlike later versions, the Windows 1.0 setup has no easily accessible settings. Instead, the executable is compiled specifically for each disk size. Furthermore, the available drivers are determined dynamically by the setup without previous configuration.

Windows 2.0 kept a similar user interface for setup as previous versions, although it introduced many back-end changes. Notably, it introduced, a plaintext configuration file, which contained a list of system files and included drivers, as well as other settings. The setup also now supports loading custom drivers from the application itself. However, Windows 2.x did not support upgrading a previous version of Windows. Any previously installed version of Windows is overwritten, and any settings must be transferred across manually from the  file.

Windows 3.x
Windows 3.0 introduced a new, more advanced installer. The black background for the setup has been replaced with a blue background with a grey bar showing the current tasks that the installation is performing. After the core Windows system files have been copied, it launches into a Windows-based GUI environment to complete Setup. From there, the remaining Windows files are copied and components are set up. This version also introduced the ability to upgrade a previously installed version of Windows by running Setup from within DOS. Upgrading a previous version transfers all its settings stored in the  file across to the newer one. Windows 3.1 introduces the ability for the user to enter their name and company.

Windows 9x
Windows 9x versions do not require an existing version of DOS to install. However, a boot disk was still required in most cases as most Windows 9x installation media was not bootable. The installation process prepares a partition, checks it using ScanDisk, and copies files to the hard disk.

In Windows 9x versions, .CAB files are used for the installation. Mostly known .CAB installation files include:


 * WIN95.CAB, WIN98.CAB and WINME.CAB: They contain the main system apps and files.
 * DRIVER.CAB: Contains the driver files for Windows.
 * NET.CAB: Contains networking and internet components.
 * MINI.CAB: Contains basic files required to start the installation from within DOS. This environment is based on Windows 3.1.

If starting the installation process from DOS, the Windows 3.1-based environment in the  file is used to start Setup. During this stage, the user configures various settings of the installation, and the Windows system files are copied to the hard disk. However, Setup can also be run from within an existing Windows 3.1 or 9x environment, skipping this portion. Once the files are copied, Setup restarts the computer, sets up devices and configures system settings.

Windows XP/Server 2003 and earlier
Since their inception, NT-based version used INF files to describe the file system layout and registry settings along with individually compressed files, similarly to other Microsoft products at the time. The user interface underwent multiple changes until its deprecation during Windows Vista development, but the key principles stayed the same. Windows NT 3.5 introduced a  program so that Setup could be started from within an existing Windows installation.

In Windows NT versions prior to Windows NT 4.0, the installation had to be booted either by running  from the respective installation directory using a boot disk, or by using boot disks provided with the installation CD. In Windows NT 4.0, the installation CD-ROM was made bootable.

Due to the operating system files being stored in the  directory on x86 architecture media, it is also often called the i386 setup, although files for other architectures used different names for the directory. Inside that directory are operating system files that are usually compressed and had their last extension character replaced with an underscore. The files use 8.3 format filenames for compatibility with MS-DOS, with the full name stored inside. Although original media usually comes with most files compressed, the compression is optional. For example, several editions of Windows XP such as Media Center Edition have files in the  directory that aren't compressed.

The installation process consists of two major phases. The first phase runs in text mode using a minimal NT environment, usually booted directly from a CD-ROM disc. It may optionally be preceded by running the Setup in an existing Windows environment or by running  from MS-DOS, which would copy the first phase environment to the boot disk and then reboot into it. It determines the hardware configuration, performs partition management, installs the core operating system and prepares for the next phase to run. The second phase runs in graphical mode and installs the rest of the operating system, as well as configures the network, date/time and asks for a product key. Starting with Windows 2000, the Network Identification Wizard runs at first boot that allows the user to configure automatic logon. This evolved into a full-on out of box experience with Windows XP, allowing the user to easily configure network settings, user accounts, and Automatic Updates.

Windows Vista/Server 2008 and later
Windows Longhorn build 4001 introduced the WIM installation format. This installation format boots the operating system via WinPE which launches the main setup user interface. The user configures multiple aspects of the installation, such as what SKU of Windows the user would like to install, what disk or partition Windows should be installed, and whether the user would like to perform an upgrade or clean installation. The setup is booted via the  file on the installation media. The install process works by deploying a pre-packed WIM image to the hard disk where Windows should be installed. However, in Windows Longhorn pre-reset builds and build 5048, the setup is also booted from the install image itself. The image index determines what SKU of Windows will be installed. From Windows 7 onwards, the DISM command line tool is used to deploy the image to the location where Windows is installed. After the WIM image is applied, the installer creates boot files on the hard disk, and restarts the machine so that devices can be set up, and the OOBE can be run. If there is an already existing version of Windows on the hard disk where the user chose to install Windows, the existing Windows installation is moved into the  directory.

Even though it was first introduced with Windows Vista, Windows XP-based Windows releases can also be packaged in WIM format. Examples can be seen in the Windows Embedded for Point of Service and Windows Fundamentals for Legacy PCs operating systems. Setup graphical assets are stored in spwizimg.dll on Windows Vista and later; Windows Longhorn pre-reset builds store them in win32ui.dll and win32uitheme.dll. Windows 8.1 introduced the ESD (Electronic Software Distribution) format. Compared to WIM, ESD files are smaller and cannot be mounted or edited without converting to WIM first.