OS Installation & Configuration

A laptop lands on your bench with a broken Windows install, and the first question is not which button to click but what has to survive: the user's files, their installed apps, both, or nothing. That one answer picks one of four install paths, and getting it wrong either destroys data you needed or wastes an afternoon rebuilding a machine you could have repaired in place. The figure below sorts the four install types by exactly that line, whether the volume is preserved or wiped, and places the two Reset this PC modes alongside them as the on-box recovery paths they are rather than as a fifth and sixth install type. This chapter owns getting an OS onto the machine: the install and recovery types, boot media, firmware and partitioning, and first-boot setup. Picking between NTFS, FAT32, and exFAT for everyday storage and keeping a running system patched belong to File Systems & Updates, and the consoles that manage disks after the install finishes are in Windows Management Tools.

The four install types

• Clean install: boot from installation media, delete or format the target partition, and lay down a fresh copy of Windows. Nothing carries over, so you reinstall every app and driver afterward. Use it for a new disk, a resale, or a machine so compromised you no longer trust the old install.
• In-place upgrade: run Windows Setup from inside the running OS (or through Windows Update) and choose to keep personal files and apps. This is the supported path from Windows 10 to Windows 11 and between Windows feature versions (Windows Setup process^[1]).
• Image deployment: capture one reference machine as an image and clone it onto many. You prepare the reference with Sysprep run with the /generalize switch, which strips the machine-specific security identifier (SID) and hardware bindings so the image is safe to duplicate (Sysprep generalize^[2]). WDS, MDT, or Microsoft Configuration Manager then push the image, commonly over the network.
• Repair installation: reinstall the same Windows version over itself to replace corrupt system files while keeping apps, settings, and data. It is an in-place upgrade pointed at the version already running.

Recovery paths that live on the machine

Two recovery options need no external media because Windows ships them on the disk. The recovery partition is a small OEM-created partition holding the Windows Recovery Environment (WinRE) and sometimes a factory image. Reset this PC (push-button reset) rebuilds Windows from those on-box files and offers two modes: Keep my files removes apps and settings but leaves personal files, and Remove everything wipes the volume, with an added data-cleaning option for a device you are handing on (push-button reset^[3]). Newer builds can also pull a fresh copy from Microsoft's servers (cloud download) instead of using the local image.

Before any upgrade: four checks

CompTIA frames upgrades around four go or no-go checks, and the exam expects you to run them before you commit:

1. Back up files and user preferences first, because even an in-place upgrade can fail.
2. Confirm application and driver compatibility, including backward compatibility for older line-of-business software.
3. Confirm hardware compatibility with the target OS.
4. Meet or exceed the minimum system requirements. For Windows 11 that floor is strict (UEFI, Secure Boot, TPM 2.0, and an approved 64-bit CPU), covered in the firmware section below.

Deciding between these types, and reading the requirement the question hands you, is the heart of A+ Core 2 objective 1.2, perform OS installations and upgrades in a diverse environment^[4].

Setup has to come from somewhere, and the source you boot from is a delivery choice, not a change to the finished OS. A single desktop takes a USB stick; a room of machines being re-imaged takes a network boot; a Mac with a wiped disk takes an internet reinstall. Match the medium to the hardware in front of you and the number of machines behind it.

The boot methods A+ expects

• USB flash drive: the everyday installer. You write a bootable Windows image to an 8 GB or larger stick (the Media Creation Tool or a Windows ISO), then boot the target from it. Fast, reusable, and the default for one-off installs.
• Optical media (CD/DVD): the same idea on a disc, now rare because images outgrew a DVD and drives are disappearing, but still listed as a method.
• Network boot (PXE): the machine's network card carries a PXE (Preboot Execution Environment) ROM that asks DHCP for an address and the name of a boot server, then pulls a small boot program over TFTP (Trivial File Transfer Protocol) and loads a WinPE (Windows Preinstallation Environment^[5]) boot image that runs Setup or applies a deployment image. This needs a server role such as WDS and is how techs image many identical PCs without carrying media to each one.
• Internet-based installation: the source lives on the vendor's servers. Windows can reinstall by cloud download during a reset, and macOS reinstalls from Internet Recovery. Useful when there is no local media and the recovery partition is gone.
• External or hot-swappable drive: boot an installer or a full OS from an external SSD or a swappable drive bay, handy for servicing or a portable environment.
• Internal drive / recovery partition: the on-box recovery partition covered earlier is itself a boot source for repair and reset.

Solid-state and flash considerations

The media you boot from and the disk you install to can both be flash. Booting from a USB flash drive is standard, and installing onto an SSD or NVMe drive is now the norm. The one gotcha is that installers on older media sometimes need the storage controller's driver loaded before they can see an NVMe disk, so keep the vendor driver handy. Where the finished disk is partitioned and formatted is the next section.

Choosing a boot method for the scenario is part of A+ Core 2 objective 1.2, perform OS installations and upgrades in a diverse environment^[4].

Two firmware modes exist, and each demands its own partition style on the boot disk: UEFI boots Windows from a GPT disk, legacy BIOS boots it from an MBR disk, and you cannot mix them for the volume Windows starts from. Get this pairing right at install time and the rest of partitioning follows; get it wrong and Setup either refuses the disk or the machine will not boot.

GPT versus MBR

MBR (Master Boot Record) is the older scheme: it stores the partition table in the first sector, tops out at four primary partitions (or three primary plus one extended holding logical drives), and cannot address a disk larger than 2 TB. GPT (GUID Partition Table), part of the UEFI standard, removes both limits: Windows supports up to 128 partitions on a GPT disk and boots disks far larger than 2 TB, and GPT keeps a backup partition table plus CRC checksums so a single corrupt sector does not lose the layout (Windows and GPT FAQ^[6]).

Trait	MBR (BIOS boot)	GPT (UEFI boot)
Max primary partitions	4 (or 3 + 1 extended)	128 in Windows
Max disk addressed	2 TB	Well beyond 2 TB
Partition table backup	None	Backup copy + CRC
Firmware to boot Windows	Legacy BIOS / CSM	UEFI

You do not have to wipe a disk to switch: mbr2gpt.exe converts a system disk from MBR to GPT in place before you flip the firmware to UEFI (mbr2gpt^[7]), while the destructive path is DiskPart's clean followed by convert gpt.

Converting a data disk to GPT with DiskPart

The command below wipes the selected disk, so use it only on a disk whose contents you can lose (a fresh install disk, never the system volume you are booted from) (DiskPart^[8]):

diskpart
list disk
select disk 1
clean
convert gpt
# ... create and format partitions from here ...

The select disk 1 line targets the second disk; confirm the number against list disk first, because clean erases whatever disk is selected.

The Windows 11 firmware floor

Windows 11 raises the bar the upgrade checklist points to: the machine must boot UEFI with Secure Boot, carry a TPM 2.0 (Trusted Platform Module), and run an approved 64-bit CPU with at least 4 GB RAM and 64 GB storage (Windows 11 requirements^[9]). Because Secure Boot and this TPM requirement are UEFI features, a compliant Windows 11 disk is always GPT. The TPM also anchors BitLocker drive encryption, which is why so many install-time questions turn on whether the firmware is UEFI. Two Microsoft tools read this floor for you, and the cheat sheet below assumes you can tell them apart: PC Health Check is a free app that tests one PC against the Windows 11 requirements and names the requirement it fails, while the Windows 11 Installation Assistant is the tool you run inside a working Windows 10 install to perform the in-place upgrade once the machine passes.

Formatting: the file system you pick at install

Formatting writes a file system onto a partition so the OS can store files. Windows installs its system volume as NTFS (New Technology File System), which adds journaling, per-file permissions (ACLs), encryption, and compression, and handles very large files and volumes (NTFS overview^[10]). Two other formats appear at install and on removable media:

• FAT32 is old and universal but limited: a single file cannot exceed 4 GB, and Windows will only format a new FAT32 volume up to 32 GB. Its one required modern job is the EFI System Partition (ESP), a small FAT32 partition (about 100 MB) the UEFI firmware reads to find boot loaders.
• exFAT removes FAT32's 4 GB file cap and is the cross-platform choice for large USB drives and SD cards that both Windows and macOS must read (exFAT specification^[11]).

A standard UEFI/GPT Windows disk therefore ends up with the layout in the figure: a FAT32 ESP (about 100 MB), a tiny Microsoft Reserved (MSR) partition (about 16 MB) with no drive letter, the NTFS Windows volume on C, and an NTFS recovery partition holding WinRE (UEFI/GPT partitions^[12]). More on NTFS versus FAT choices and update servicing lives in File Systems & Updates; the disk tools that create these partitions after install are in Windows Management Tools. Partition schemes and formatting are core to A+ Core 2 objective 1.2, perform OS installations and upgrades in a diverse environment^[4].

Hand a technician a MacBook to wipe, a spare laptop to put Linux on, and a new iPhone to set up, and the same install-and-configure logic covers all three with different tools. The pattern holds everywhere: choose a source, lay down the OS, pick a file system, then run first-boot setup.

macOS

A Mac reinstalls from macOS Recovery rather than a USB stick in most cases. On Apple silicon you hold the power button to reach recovery; on older Intel Macs you hold Command-R at boot, and Internet Recovery downloads the installer when the local one is gone. Disk Utility in Recovery erases and formats the disk, and the modern format is APFS (Apple File System), the default since macOS High Sierra and the right choice for SSDs; older or mechanical drives may still use Mac OS Extended (HFS+). Migration Assistant then moves apps, accounts, and files from another Mac, a Time Machine backup, or a Windows PC during setup. The App Store and Software Update handle patches after that.

Linux

Most Linux installs boot from a live USB: you write a distribution image (Ubuntu, Fedora, and others) to a stick, boot it, try the desktop, then run the installer. The installer partitions the disk, commonly ext4 for the root file system with a swap partition or swap file, and on a machine that already runs Windows it can install alongside it. That dual-boot setup leaves Windows in place and installs the GRUB boot loader, which shows a menu at power-on to pick Windows or Linux. Package managers such as apt and dnf install and update software afterward.

Mobile operating systems

Phones and tablets run a guided first-boot setup assistant rather than a disk installer, because the OS ships on the device. iOS and iPadOS setup walks through language, region, Wi-Fi, an Apple ID, Face ID or Touch ID, and a restore from an iCloud or computer backup, then activates the device with the carrier. Android setup mirrors this with a Google account, a screen lock, and a restore from a prior device or cloud backup. In a managed workplace, both enroll into mobile device management (MDM) during setup, which pushes configuration and apps automatically. Recognizing these cross-platform equivalents is part of A+ Core 2 objective 1.2, perform OS installations and upgrades in a diverse environment^[4].

The install is not done when files finish copying; it is done when the out-of-box experience (OOBE) finishes and the desktop loads ready to use. OOBE runs in a fixed order on first boot, and each step is a support decision, as the figure lays out: localization, network, account, privacy, and updates.

Localization

The first screens set localization: country or region, the display language, one or more keyboard layouts, and the time zone and date/time format. These are easy to click past and annoying to fix later, since a mismatched keyboard layout types the wrong symbols, so set them correctly the first time.

Network

OOBE asks the machine to join a network next, over Wi-Fi or Ethernet. Connectivity matters here because the later steps depend on it: Windows 11 Home requires an internet connection and a Microsoft account to finish setup (Windows 11 requirements^[9]), and updates cannot download without it.

The account decision

Choosing the first account type is the configuration choice with the longest reach:

• Local account: credentials stored only on that PC, with no cloud sync. Simple, offline, common for shared or lab machines.
• Microsoft account (MSA): a cloud identity that syncs settings and unlocks Store and OneDrive features; the default on Home.
• Domain join: the PC joins an on-premises Active Directory domain, so users sign in with domain credentials and administrators manage it by policy. Requires Windows Pro or higher.
• Microsoft Entra join: the cloud equivalent of a domain join for organizations that manage identity in Microsoft Entra ID (Entra device identity^[13]), also Pro or higher.

Do not confuse a Microsoft account, which is one person's cloud login, with a domain or Entra join, which is an organization taking management of the device; questions lean on that distinction. Between the account and updates, OOBE also offers privacy and sign-in options (telemetry, location, and a Windows Hello PIN); accept or tighten these per policy.

Updates

The last OOBE step, and the first thing to do on any fresh or newly imaged machine, is Windows Update. A freshly installed image is months behind on security patches, so it pulls cumulative updates, and often driver and feature updates, before the machine is trustworthy on the network (how Windows Update works^[14]). Ongoing update servicing and channels are covered in File Systems & Updates.

Localization, network, account type, and updates map to the settings groups A+ Core 2 objective 1.6 lists as Time and Language, Network and Internet, Accounts, and Update and Security (exam objectives^[4]).

A+ install questions rarely ask for a definition; they hand you a scenario with a constraint and ask what to do FIRST or NEXT. The winning move is to name the constraint (data must survive, disk over 2 TB, Windows 11 required, many machines) and pick the option that respects it, then reject the option that ignores it.

How the stems read

Question stem says	Right answer	Common wrong answer
Move Windows 10 to 11, keep apps and files	In-place upgrade	Clean install, which discards apps and files
Windows 11 upgrade is blocked	Machine lacks TPM 2.0, Secure Boot, or UEFI	Add RAM, which is not the failing check
Deploy 40 identical lab PCs	Image deployment (Sysprep + PXE)	Installing each one by hand from USB
Boot disk is 3 TB but only 2 TB is usable	Disk is MBR; use GPT under UEFI	Replace the drive, which is not the fault
Repurpose a PC for another user, wipe data	Reset: Remove everything or clean install	Reset: Keep my files, which leaves data behind
OS is corrupt but user data must stay	Repair installation or Reset: Keep my files	Clean install, which erases the data
Freshly imaged PC before handover	Run Windows Update first	Going straight to production use
USB installer cannot see the NVMe disk	Load the storage controller driver	Reformatting, which the installer cannot reach yet

Each row rewards reading the stated constraint literally: the drive count, the 2 TB ceiling, the TPM check, or the words keep versus remove. Naming the constraint first, then matching the install type or partition scheme to it, is the whole skill A+ Core 2 objective 1.2, perform OS installations and upgrades in a diverse environment^[4], tests here. When the corruption runs deeper than a reinstall fixes, the next stop is OS and application troubleshooting.