Quick Guide to Installing Linux as an Alternative to Windows

Installing Ubuntu alongside Windows takes about forty minutes, and roughly thirty-five of those are waiting. The risky part is the five minutes before you start, and most guides skip it entirely — which is how people end up with a Windows partition that will not boot.

This walks through the whole thing, including the three preparation steps that actually prevent data loss and the clock bug that will otherwise confuse you for a week afterwards.

Before you touch anything

Back up your files. You are about to resize the partition your operating system lives on. That operation is routine and it is also the one place in this process where a power cut costs you everything. An external drive or a cloud sync is fine; a second partition on the same disk is not.

Check whether your drive is encrypted. Windows 11 turns on device encryption by default on most machines, and shrinking an encrypted volume can leave you locked out with no recovery key to hand. Open Settings and search for "device encryption" or "BitLocker". If it is on, either suspend it before you start, or save the recovery key somewhere that is not the machine you are about to repartition.

Turn off Fast Startup. This is the single most common cause of a broken dual boot, and it is invisible until it bites. When Windows "shuts down" with Fast Startup enabled it actually hibernates, leaving the filesystem marked as in use. Linux then either refuses to mount your Windows drive or, worse, mounts it anyway and corrupts it.

Control Panel → Power Options → Choose what the power buttons do → Change settings that are currently unavailable → untick Turn on fast startup.

Do that now, not later.

Step 1: Choose a distribution

Ubuntu is the sensible default for a first install: the hardware support is broad, and when something goes wrong the error message you paste into a search box has probably been answered a thousand times. That last property matters more than any feature comparison.

Take the latest LTS release. LTS means Long Term Support — five years of security updates instead of nine months. The non-LTS releases are for people who want newer packages and are willing to reinstall regularly.

Download the desktop ISO from ubuntu.com. It is around 5GB.

Step 2: Verify the download

Skipping this is usually fine and occasionally catastrophic. A truncated download produces an installer that fails halfway through writing to your disk, which is a much worse place to discover the problem.

Ubuntu publishes a SHA256SUMS file next to the ISO. In PowerShell:

Get-FileHash -Algorithm SHA256 .\ubuntu-24.04.3-desktop-amd64.iso

Compare the result against the published sum — they should match exactly. Any hash generator will do the same job if you would rather not use the command line.

Step 3: Make room for Linux

The installer can resize your Windows partition itself, but doing it from Windows first is safer, because Windows understands its own filesystem better than anything else does.

1. Right-click the Start button → Disk Management
2. Right-click your main partition (usually C:) → Shrink Volume
3. Enter the space to free up, in megabytes

Give Ubuntu at least 40GB if you intend to use it properly. 25GB works but you will be deleting things within a month. Leave the freed space unallocated — do not create a new volume in it. The Ubuntu installer wants raw space.

If Windows refuses to shrink as far as you expect, that is usually immovable system files. Disabling hibernation temporarily (powercfg /h off in an administrator prompt) frees a block equal to your RAM and often unblocks it.

Step 4: Create the bootable USB

Download Rufus and insert a USB drive of 8GB or more. Everything on it will be erased.

The settings that matter:

If Rufus offers to download additional files when you press Start, let it. Choose Write in ISO Image mode if prompted.

Getting the partition scheme wrong is the usual reason a USB stick does not appear in the boot menu. If yours does not, this is the first thing to re-check.

Step 5: Boot from the USB

There are two different keys people confuse here. The boot menu is a one-time choice of device, usually F12, F11 or Esc. The firmware setup (what people still call the BIOS) is usually Del or F2, and is where you change the permanent boot order. You want the boot menu.

Modern machines boot too fast to catch either. The reliable route is from Windows: hold Shift while clicking Restart, then Use a device, or Troubleshoot → Advanced options → UEFI Firmware Settings.

On Secure Boot: Ubuntu is signed and boots with Secure Boot enabled, so you should not need to disable it. If you plan to install proprietary drivers, the installer will ask you to set a password and confirm a key on the next reboot. That screen appears once, looks alarming, and is normal.

Step 6: Install

Choose Try Ubuntu rather than installing straight away. It costs two minutes and tells you whether your Wi-Fi, trackpad and display work before you commit anything to disk. If the Wi-Fi does not work in the live session, it will not work after installing either — worth knowing now, with Windows still intact.

When you run the installer:

1. Language and keyboard layout
2. Normal installation, and tick Install third-party software — this covers Wi-Fi chipsets, graphics drivers and media codecs
3. At the installation type screen, choose **Install Ubuntu alongside Windows Boot Manager**

That third step is the one to read twice. The options next to it are Erase disk and install Ubuntu, which deletes Windows, and Something else, which is manual partitioning. If "alongside" is not offered, stop: it usually means the installer did not find your unallocated space or your drive is still encrypted. Do not proceed with Erase disk to make the error go away.

Set a username and password, and let it run. Remove the USB stick when prompted.

Step 7: Fix the clock

Here is the one nobody warns you about. After a dual-boot install, Windows and Linux disagree about what time it is — typically by whatever your timezone offset is.

The cause: Windows assumes the hardware clock stores local time, while Linux assumes it stores UTC. Each one "corrects" the clock on boot, and they undo each other.

Fix it once, from Linux, by telling it to use local time as Windows does:

timedatectl set-local-rtc 1 --adjust-system-clock

Then check it took:

timedatectl

Look for RTC in local TZ: yes. Both systems will now agree.

When it goes wrong

The USB does not appear in the boot menu. Almost always the Rufus partition scheme. Rewrite it as GPT/UEFI.

Windows no longer boots. Fast Startup was left on, or the boot order changed. Enter firmware setup and check that Windows Boot Manager is still listed. GRUB should offer both systems; if it boots straight to Ubuntu, run sudo update-grub from Ubuntu to make it re-detect Windows.

No Wi-Fi after installing. Usually a proprietary driver. Connect by ethernet or USB tethering, then open Additional Drivers and install what it offers.

You want Windows back. From Windows: delete the Ubuntu partition in Disk Management, extend C: into the free space, then repair the bootloader from a Windows recovery USB with bootrec /fixmbr. Do it in that order.

Summary

The install itself is a wizard. What makes dual-booting go badly is almost never the installer — it is Fast Startup left enabled, an encrypted drive nobody checked, or a USB written with the wrong partition scheme. Handle those three and the rest is waiting for a progress bar.