Reinstalling an operating system, without the guesswork
Step-by-step walkthroughs for Windows 11 and macOS, written against the vendors’ own documentation. Every download link on this site points at Microsoft’s or Apple’s servers — there are no mirrors, no repacks, and no activation utilities hiding further down the page.
Reinstall Windows 11
From deciding whether you need a clean install at all, through building the USB stick, the BIOS keys that actually work, and the partition screen that destroys data if you misread it.
- Back up
- Official ISO
- USB media
- Boot menu
- Partitioning
- Drivers
- Activation
Reinstall macOS
Apple silicon and Intel behave differently at almost every step. This covers both, and separates a reinstall — which keeps your files — from a clean install, which does not.
- Time Machine
- Recovery mode
- Apple silicon vs Intel
- Disk Utility
- Migration Assistant
Back up first, and test the backup
A clean install does not warn you a second time. Both guides assume you have a backup that you have opened and restored a file from — not one you merely made.
- Windows: copy anything irreplaceable to an external drive or cloud storage, and check the copies open. File History, OneDrive and a plain external drive all work; a backup on the disk you are about to erase does not.
- macOS: run System SettingsGeneralTime Machine to an external drive and let it finish. Then open the drive and confirm your files are on it.
- Both: note down your licence information. For Windows that means a Microsoft account with the digital licence attached, or a 25-character key. For macOS it means your Apple Account password, which Recovery will ask for.
- Both: if the drive is encrypted, find the recovery key before you start. After a clean install without it, the data is unrecoverable at any price.
Official images, and nothing else
Microsoft and Apple are the only vendors here. The full list includes evaluation images, developer builds, and Microsoft’s own instructions for its media-creation tool.
Why this site has no mirror list
Most reinstall guides in any language end with a table of third-party download sites. The reasoning is convenience: one place, every version, faster servers. The cost is that you cannot tell whether the image you got was modified, and modified installation images are one of the few ways malware survives a full reinstall.
- A modified installer defeats the reinstall. Reinstalling is the standard answer to “my machine is infected”. Installing from a repackaged image starts the new system with whatever the packager added, and it inherits the reputation of the vendor it is impersonating.
- “Clean” and “optimised” are marketing words, not verifiable claims. A trimmed image is not the image the vendor shipped, so vendor support, activation and update behaviour all become your problem.
- Every link here resolves to the vendor's own domain. If you wanted to verify that, you can: hover the link and read the hostname. There is no redirect layer, no shortener, and no affiliate parameter on this site.
What about checking a hash?
Good instinct, and it is the one reliable protection — but only when you have an authoritative hash to compare against. Vendors do not consistently publish them for consumer images, and a hash listed on the same page as a download proves nothing. Buying a genuine key and downloading from the vendor is stronger, and simpler, than verifying a copy of unknown provenance.
Read this before you erase anything
The walkthroughs cover the steps. These 10 guides cover the decisions in front of them: whether a clean install is needed at all, how to prove a backup restores, what the partition screen is showing, and what to do when the same fault survives a reinstall. Each one cites the vendor documentation it was checked against.
Do you need a clean install at all?
Reset this PC, an in-place upgrade, a reinstall and a clean install are four different operations. Choosing the wrong one costs an afternoon, or your files.
A backup you can actually restore
A backup that has never been opened is a guess. How to make one, how to test it, and the recovery keys you need before erasing an encrypted disk.
Secure Boot, TPM 2.0 and the Windows 11 requirements
Why disabling Secure Boot is the wrong fix, what TPM 2.0 actually does, and how to check both before you build installation media.
Building installation media that actually boots
Media Creation Tool, a direct ISO and a USB writer, or Apple's createinstallmedia: what each is for, and the sizing and formatting mistakes that waste an afternoon.
The Windows partition screen, read slowly
The one screen in Windows setup where a misread label destroys data. What 'Drive 0 Partition 1' means, which entries belong to Windows, and when to stop and unplug drives.
Drivers and activation after a clean Windows install
What Windows Update already handles, when a vendor driver is genuinely needed, and how a digital licence reattaches to the same hardware without a key.