Installing and Upgrading an OS

Planning an installation

Installing an operating system takes an hour; recovering from a badly planned installation can take days. Before you boot from any installation media, answer three questions: can this hardware run the new system, will the user's software and devices still work afterward, and is the data safe if something goes wrong?

System requirements

Every operating system publishes minimum hardware requirements. Windows 11 is stricter than its predecessors, mainly because it relies on hardware security features. Microsoft's minimums are:

The processor list is the requirement that surprises people: a fast, perfectly working PC from 2017 can fail it. The supported lists roughly start with Intel's 8th-generation Core processors and AMD's Ryzen 2000 series. TPM 2.0 is often present but switched off in the firmware (as Intel Platform Trust Technology, PTT, or AMD firmware TPM, fTPM), and Secure Boot may be disabled; both are settings, not hardware you have to buy. See BIOS, UEFI and Boot for where to find them. Microsoft's PC Health Check app tests a machine against all requirements and names the ones it fails.

Windows 11 exists only as a 64-bit operating system. The installation also expects an internet connection for Home and Pro (personal use), and at the time of writing Microsoft keeps adjusting the account rules for setup (see accounts during setup).

Checking a whole fleet is a job for a script, not for a clipboard. The logic is a list of rules applied to each machine's inventory data:

MIN_RAM_GB = 4
MIN_STORAGE_GB = 64

pcs = [
    {"name": "HR-LAPTOP-07", "cpu_ok": True, "ram_gb": 16, "storage_gb": 512,
     "tpm": "2.0", "uefi_secure_boot": True},
    {"name": "RECEPTION-PC", "cpu_ok": False, "ram_gb": 8, "storage_gb": 256,
     "tpm": "1.2", "uefi_secure_boot": True},
    {"name": "WAREHOUSE-01", "cpu_ok": False, "ram_gb": 2, "storage_gb": 32,
     "tpm": None, "uefi_secure_boot": False},
]


def problems(pc):
    found = []
    if not pc["cpu_ok"]:
        found.append("CPU not on the supported list")
    if pc["ram_gb"] < MIN_RAM_GB:
        found.append(f"{pc['ram_gb']} GB RAM, needs {MIN_RAM_GB}")
    if pc["storage_gb"] < MIN_STORAGE_GB:
        found.append(f"{pc['storage_gb']} GB storage, needs {MIN_STORAGE_GB}")
    if pc["tpm"] != "2.0":
        found.append(f"TPM {pc['tpm'] or 'missing'}, needs 2.0")
    if not pc["uefi_secure_boot"]:
        found.append("no UEFI with Secure Boot")
    return found


for pc in pcs:
    issues = problems(pc)
    if issues:
        print(f"{pc['name']}: {len(issues)} problem(s)")
        for issue in issues:
            print(f"  - {issue}")
    else:
        print(f"{pc['name']}: meets the minimum requirements")

HR-LAPTOP-07: meets the minimum requirements
RECEPTION-PC: 2 problem(s)
  - CPU not on the supported list
  - TPM 1.2, needs 2.0
WAREHOUSE-01: 5 problem(s)
  - CPU not on the supported list
  - 2 GB RAM, needs 4
  - 32 GB storage, needs 64
  - TPM missing, needs 2.0
  - no UEFI with Secure Boot

RECEPTION-PC is the typical case: enough memory and storage, but too old a processor. Microsoft documents a way to install Windows 11 on such hardware anyway, but those devices are unsupported and are not guaranteed to receive updates, which makes them a poor choice in a business. The honest answer is usually replacement. With Windows 10 past its end of support (October 14, 2025), that decision can no longer be postponed for free: consumer Extended Security Updates (ESU) run only until October 2026.

Application and driver compatibility

Hardware that meets the minimums can still be a bad candidate. Ask before the installation, not after:

• Applications: is every business application supported on the new version? Line-of-business software, old accounting packages and anything that talks to special hardware are the usual problems. Check the vendor's support statement.
• Drivers: do printers, scanners, docking stations and specialized devices (label printers, card readers, lab equipment) have drivers for the new system? A device without a driver is a device that no longer works.
• Architecture: a 32-bit application usually runs on 64-bit Windows, but a 32-bit driver never does.

In an organization, the answer comes from a test: upgrade a few pilot machines, used by real users for real work, before rolling out to everyone.

Back up first

Every installation can go wrong: a power cut halfway through an upgrade, the wrong disk selected in setup, a driver that prevents booting. Before you start, back up the user's data and write down what you would need to rebuild the machine: installed applications, license keys, mapped network drives, printers, browser bookmarks and email settings. For a clean install this is not optional, because the old disk contents will be gone. See Backup and Recovery.

Clean install, upgrade or repair

A clean install erases the target partition (usually the whole disk) and installs the operating system from scratch. Nothing of the old system survives: no files, no settings, no applications, and also none of the old problems. An in-place upgrade installs the new version over the old one and carries over the user's files, settings and applications. A repair install is an in-place upgrade to the same version: it replaces all system files while keeping data and apps, which fixes a damaged installation without starting over.

An in-place upgrade from Windows 10 to 11 runs through Windows Update when the PC is eligible, or by starting setup.exe from mounted installation media. Setup then offers to keep personal files and apps, only personal files, or nothing. Keeping apps is only possible when the architecture and language match; a 32-bit Windows 10 cannot be upgraded in place to Windows 11, because Windows 11 is 64-bit only. After an upgrade, the old installation stays in C:\Windows.old, and Settings offers to go back to the previous version for 10 days.

For a repair install, recent Windows 11 versions offer Fix problems using Windows Update under Settings > System > Recovery, which reinstalls the current version while keeping apps, files and settings. Running setup.exe from media of the same version does the same. Reset this PC, on the same page, is closer to a clean install: it reinstalls Windows and removes apps, optionally keeping the user's files.

Boot methods and installation media

To install an operating system you have to start the computer from something other than its own disk. The firmware's boot menu (often F12, F11, Esc or F8 during startup, depending on the manufacturer) picks the device for one boot without changing the permanent boot order.

• USB (Universal Serial Bus) flash drive: the standard today. Microsoft's Media Creation Tool downloads Windows 11 and writes it to a USB drive of at least 8 GB (or saves an ISO file). An ISO is a disk image file of an installation DVD; the open-source tool Rufus writes any ISO, including Linux ones, to a bootable USB drive.
• Network boot: with PXE (Preboot Execution Environment), the network card's firmware gets an Internet Protocol (IP) address from a Dynamic Host Configuration Protocol (DHCP) server, is told where to find a boot image, and downloads it from a deployment server. No media needs to touch the machine, which is how organizations reinstall hundreds of PCs.
• Optical disc: DVDs still work where there is a drive, but they are rare and slow.
• Recovery partition: many PCs come with a hidden partition from the manufacturer that can restore the factory installation.
• Internet-based: macOS Recovery and some PC manufacturers can download and reinstall the system directly from the internet.

Installing Windows step by step

A clean installation of Windows 11 from USB follows the same path on almost every PC:

1. Boot from the USB drive and choose language, keyboard layout and the option to install Windows.
2. Enter a product key, or choose "I don't have a product key" when the PC already has a digital license or an OEM (original equipment manufacturer) key in its firmware (see licensing).
3. Choose the edition, if the media offers several.
4. Accept the license terms.
5. Choose the disk and partitions to install on (below).
6. Setup copies files and restarts several times. Leave the USB drive in, but do not boot from it again.
7. The out-of-box experience (OOBE) asks for region, keyboard, network, account and privacy settings.

Partitioning during setup

For a clean install, delete the old partitions on the target disk until it shows as unallocated space, select that space, and let setup create the partitions it needs. On a UEFI computer, setup initializes the disk with a GUID Partition Table (GPT) and creates this layout:

Partitioning and formatting are explained in Disks, Partitions and Volumes. Two practical points belong here. First, check twice which disk you are deleting partitions on: in a PC with two drives, the data drive is one click away. Second, if setup shows no disks at all, the storage controller needs a driver that is not on the media (common with Intel Volume Management Device (VMD) or RAID (redundant array of independent disks) controllers): download it from the manufacturer and use Load driver in the disk selection screen.

Accounts during setup

During OOBE, Windows asks who will use the PC. The options depend on the edition and on whether the PC is personal or for work:

• Microsoft account: an online account (an Outlook or other email address) that syncs settings, enables OneDrive and stores the BitLocker recovery key. At the time of writing, Windows 11 Home and Pro setup for personal use expects an internet connection and a Microsoft account, and Microsoft has been removing the known workarounds for creating a local account during setup. Check current behavior before promising a user a local account.
• Work or school account: on Pro and higher, "Set up for work or school" signs in with a Microsoft Entra ID account and enrolls the PC in the organization's management.
• Local account: exists only on this PC. Still possible after setup (Settings > Accounts > Other users), and in unattended installations.

Joining an on-premises Active Directory domain happens after setup, on Pro, Enterprise or Education; see Windows Essentials. Account types and rights are covered in Users, Permissions and Access Control.

Imaging and deployment

Installing and configuring fifty PCs by hand takes fifty times as long and gives fifty slightly different results. Organizations therefore deploy operating systems. The classic method is a disk image: a file that contains the complete contents of a partition or disk, including the operating system, applications and settings, which can be written to other computers.

1. Install and configure one reference computer: Windows, updates, standard applications, settings.
2. Run Sysprep (System Preparation Tool, C:\Windows\System32\Sysprep\sysprep.exe) with /generalize /oobe /shutdown. Generalizing removes what must be unique per machine: the computer's security identifier (SID), its name, driver state and activation state. On the next start, the PC goes through OOBE as if it were new.
3. Capture the generalized system into an image file (Windows uses the Windows Imaging Format, WIM), and deploy it to target PCs over the network (PXE) or from USB.

Cloning copies a disk sector by sector to another disk. That is fine for moving one PC to a new drive, but cloning a non-generalized Windows installation onto many PCs is not supported by Microsoft: every copy has the same SID and name, which causes conflicts in a domain.

Images age quickly, because every month of updates and every new application version means a new image. Modern management therefore often skips imaging. With Windows Autopilot, the manufacturer or reseller registers the device's hardware ID with the organization's Microsoft Intune tenant. The new PC is shipped directly to the user, who connects to the internet and signs in with a work account; Autopilot then turns the factory installation into a managed, configured company PC, and Intune installs the apps.

Unattended installation

An unattended installation answers setup's questions from a file instead of from a person at the keyboard. For Windows, the answer file is an XML (Extensible Markup Language) file. When a file named autounattend.xml is in the root of the installation USB drive, setup picks it up automatically and can partition the disk, select the edition, accept the license, set the language and time zone, create accounts and run commands. The same format, usually named unattend.xml, is passed to Sysprep to automate OOBE after an image is deployed.

Answer files are created with Windows System Image Manager, part of the Windows Assessment and Deployment Kit (ADK). Linux distributions have the same idea under other names, such as Kickstart for Red Hat and cloud-init for cloud servers.

Dual boot

A dual boot setup has two operating systems installed on one computer, each on its own partition or disk, and a boot manager that asks at startup which one to start. Windows Boot Manager can choose between Windows installations; Linux usually installs GRUB (GRand Unified Bootloader), which also detects Windows and adds it to its menu.

The usual order is Windows first, then Linux: the Linux installer recognizes Windows and adds it to the menu, whereas Windows setup ignores other operating systems. Dual boot comes with risks a technician should mention:

• Resizing partitions to make room is a moment where data can be lost. Back up first.
• Windows updates can reset the firmware's boot order or replace boot entries, after which the other system seems to be gone.
• With BitLocker enabled, changes to the boot configuration can trigger a request for the BitLocker recovery key. Make sure it is available before you start.
• Windows Fast Startup leaves the NTFS partition in a hibernated state; changing files on it from Linux can corrupt them.
• The two systems may interpret the hardware clock differently (Windows as local time, Linux as Coordinated Universal Time, UTC), so the clock jumps after switching.

For testing or running a second system, a virtual machine is usually the better choice: no partitioning, no boot manager, and both systems run at the same time. Virtualization is covered in the Cloud topic.

Licensing and activation

A license is the right to use the software; for Windows it comes in three main channels:

Product activation is the check that links a valid license to a specific device, so that one key cannot be used on unlimited PCs. Windows activates online, using a 25-character product key or a digital license: a record at Microsoft that this hardware is entitled to Windows, for example after a free upgrade or an OEM installation. A digital license needs no key during reinstallation; the PC activates automatically once it is online. If the digital license is linked to the user's Microsoft account, the Activation troubleshooter can reactivate after a major hardware change such as a new motherboard.

Organizations activate differently. A Multiple Activation Key (MAK) activates a set number of PCs online. Key Management Service (KMS) and Active Directory-based activation let PCs activate against the organization's own infrastructure, and must renew that activation periodically. The state of any PC is under Settings > System > Activation, or on the command line with slmgr /xpr.

macOS and Linux installation

macOS is installed only on Apple hardware, and its installation is mostly automatic. Upgrades arrive through Software Update in System Settings. To reinstall, start macOS Recovery and choose Reinstall macOS, which downloads the system from Apple; this keeps the user's data unless you erase the disk first with Disk Utility. A bootable USB installer can be made with the createinstallmedia command included in the installer app. Apple silicon Macs run only macOS natively; Boot Camp, Apple's tool for installing Windows on a Mac, exists only on Intel Macs. See macOS Essentials.

Linux is downloaded as an ISO from the distribution's website and written to a USB drive (with Rufus, balenaEtcher or the dd command). Most distributions boot into a live session first, so you can check that the hardware works before installing anything. The installer handles partitioning (with an option to install alongside Windows), the user account and the time zone. Mainstream distributions such as Ubuntu and Fedora boot with Secure Boot enabled; others may require turning it off. Most Linux distributions cost nothing and need no activation; enterprise distributions such as Red Hat Enterprise Linux are sold as subscriptions. See Linux at a Glance.

After the installation

A freshly installed system is not finished. A technician's checklist:

1. Updates: run Windows Update until nothing new appears; installation media is often months old. See Updates, Patches and Drivers.
2. Drivers: check Device Manager for devices with a warning icon, and install chipset, graphics and network drivers from the manufacturer where Windows Update has none.
3. Activation: confirm that Windows is activated.
4. Security: Microsoft Defender and the firewall on, BitLocker or device encryption on (and the recovery key stored safely), the user working as a standard user where policy requires it.
5. Applications: install the standard and user-specific software.
6. User data and settings: restore files from the backup, reconnect OneDrive, printers, mapped drives and email.
7. Verify with the user: can they log in, open their files and do their work? Then document what was done in the ticket.