If you want to reinstall Windows on your computer from scratch, you will need the product key that came with your computer or copy of Windows. However, if you don’t have a copy of Windows to install, you will have to find a copy of it for yourself. If you didn’t already know this, Microsoft does offer free ISO files for you to download, so here’s what you have to do to find and install them.

Windows Media Creation Tool
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Finding a legal copy of Windows

If you want a legit copy of Windows there are a few different ways you can go about getting one. This means you won’t have to visit a shady BitTorrent website to download a copy. Instead, you will get a legitimate and official copy of your chosen version of Windows, straight from Microsoft.

There is a chance you could find yourself having some problems when and if you try to use an OEM key with a retail version of Windows. If you find yourself in this situation, it means that Windows will not activate. The only solution for this is to call Microsoft and have customer service activate your copy of Windows.

Downloading Windows 10 or 8.1 ISO with the media creation tool

The official way to download an ISO for Windows 10 or 8.1 on a computer is to use the media creation tool. The actual process for using it is basically the same for both versions of Windows, so in this tutorial, I will be using the Windows 10 media creation tool. Before I move on, I need to tell you that there is no longer an ISO available for Windows 8. So if you have a product key for Windows 8, you can’t use it to install Windows 8.1. What you will have to do is upgrade to Windows 8.1.

Starting with the download instructions, you can download either the Windows 10 media creation tool or the Windows 8.1 media creation tool. As soon as your chosen file has finished downloading, double-click it to run the tool and then click YES. This will give it permission to make changes to your computer. When the tool starts up, click ACCEPT to accept the terms of the license. The only difference between the two versions is that the Windows 8.1 tool will not ask you to accept the license terms.

Windows 10 License
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Next, the tool will ask you want you want to do. You should select Create installation media for another PC, and then click NEXT. Again, there are differences between Windows 10 and 8.1 here. The 8.1 version will not ask you if you want to do anything. Instead, it automatically creates the installation media for another computer.

The tool will now suggest a language, architecture, and edition for your version of Windows based on the information it has gathered about the computer it is running on. If you’re going to use the media you’re creating on that computer, you just need to click NEXT. However, if you plan to use the copy of Windows on another computer, clear the option Use recommended options for this PC check box.

You should now select the options that are more appropriate for the license you have, and then click NEXT. Again, there is a difference between the two versions of Windows. Windows 8.1 will actually show you this screen from the start, plus it will not recommend any options; you will have to choose them for yourself.

Using the correct license

Before we go any further, it is worth reminding you that your license will only work with the correct version assigned to it., meaning that if your license is for 64-bit Windows 10 Pro, it will not work with a 32-bit Windows 10 version. So please make sure your selections match what is listed with your product key.

Download install Windows
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USB, flash drive or ISO file

Next, it is time to decide whether you want to use the tool to create a bootable USB flash drive or just create an ISO file that you can use to burn to a DVD at a later date. In this tutorial, I have chosen to go with an ISO file; however, the process is basically the same whichever option you choose.

If you choose to go with the USB option, you will need your own USB drive with a minimum of 3GB of free space. If you choose this option, please back up all the data on the USB drive, as it will be formatted during the process. Once you have done the above, select your chosen option and then click NEXT.

Now you will be asked for a place to save the completed ISO file (or point the tool toward the right USB drive if you chose that option). It is now that the media creation tool will start to download the required files and create the ISO file. At this point, you must be patient, as this can take some time to complete. However, it depends on your Internet connection speed. Once it has finished doing its work, you can click OPEN DVD BURNER and create a disk straight away or click FINISH and create the disk later.

Your options

So now that you have a new Windows ISO file saved, your options are to go and perform a clean install of Windows on your computer (which technically you really don’t need a product key to do), or you could use the ISO to create a virtual machine or simply save it for later use.