This article teaches you how to remove and reinstall the operating system on a Windows or Mac computer. Doing so is typically a response to a corrupt or infected operating system. Before re-imaging your computer, your should back up your data to an external hard drive.

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On Windows

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    Open Start 

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    . Click the Windows logo in the bottom-left corner of the screen.

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    Open Settings 

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    . Click the gear-shaped icon in the lower-left side of the Start window.

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    Click 

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    Update & Security. This icon is near the bottom of the Settings window.

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    Click the Recovery tab. It’s on the left side of the window.
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    Click Get started. You’ll find this option below the “Reset this PC” heading near the top of the page.
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    Click Remove everything when prompted. It’s at the top of the pop-up window.
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    Click Remove files and clean the drive. This option will completely erase your computer’s hard drive and then reinstall Windows 10 on it.

    • You may see a warning about not being able to roll back to a previous version of Windows here. If so, click Next before continuing.
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    Click Reset when prompted. Your computer will begin resetting itself.
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    Wait for Windows to finish resetting. The reset process can take several hours to complete, so just make sure that the computer is plugged into a reliable power source to ensure that it doesn’t shut down.
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    Click Continue when prompted. Once your computer finishes resetting, you’ll see this at the top of the page. Clicking it will take you to the setup page.
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    Follow the on-screen prompts. You’ll select a language, connect to a Wi-Fi network, and perform other setup tasks to complete the Windows 10 reinstallation.

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On Mac

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    Open the Apple menu 

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    . Click the Apple logo in the top-left corner of the screen. A drop-down menu will appear.

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    Click Restart…. It’s near the bottom of the drop-down menu.
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    Click Restart when prompted. Your Mac will begin to restart.
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    Place your Mac in recovery mode. Immediately after clicking Restart, press and hold the  Command key and the R key simultaneously until greeted by the “Utilities” window.
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    Select Disk Utility. It’s the grey hard drive-shaped icon in the main window.
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    Click Continue. This is in the bottom-right corner of the window.
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    Select your Mac’s hard drive. On the left side of the window, click the hard drive on which your Mac’s operating system is installed.
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    Click Erase. It’s a tab at the top of the window. A pop-up window will appear.
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    Click the “Format” drop-down box. You’ll find this on the right side of the page. Doing so prompts a drop-down menu.
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    Click Mac OS Extended. It’s in the drop-down menu.
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    Click Erase. This is in the bottom-right corner of the window.
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    Wait for your Mac’s hard drive to finish erasing. The erasing process will take some time, so just make sure that your Mac is plugged in and charging to prevent it from accidentally dying.
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    Click Done when prompted. Doing so completes the erasing process.
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    Click Disk Utility. This menu item is in the top-left side of the screen.
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    Click Quit Disk Utility. It’s at the bottom of the Disk Utility drop-down menu. Doing so returns you to the main Recovery window.
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    Select Reinstall macOS, then click Continue. MacOS Sierra will begin reinstalling itself on your hard drive.
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    Follow the on-screen prompts. Once MacOS Sierra has been reinstalled, you can proceed with setting up your Mac (e.g., choosing a language and connecting to Wi-Fi).