If you have a Windows 7 or 8 computer, you have until July 29 to upgrade it to Windows 10 for free. While your data, apps and most of your system settings will remain intact, upgrading tends to adversely affect performance.

This post will show you how to change that and get a clean install of Windows 10 onto your computer. This is possible both after you've already upgraded to Windows 10 and before, when your computer still runs Windows 7 or 8.

Important note: You can't get a fresh system install without all of your apps and possibly some personal data being erased, so make sure to back up all of your important information before you begin this process. If you want to learn more about preparing your computer for Windows 10 (including how to backup), check out this post.

For a system already running Windows 10

If your computer already runs Windows 10, the easiest way to refresh the machine is to reset it.

Step 1: From the Windows 10 Start Menu, click on Settings.

Step 2: On the Settings page, click on the button that reads Update & security.

Step 3: Now on the update and security page, click on Recovery, then under Reset This PC,click on Get Started.

Step 4: Choose the provided option to Remove everything. Alternatively, you can choose to retain your personal files (such as those in the Desktop and Documents folders) which will keep the files in your profile intact.

Note that the last option, Restore factory settings, is only available in certain machines and will reinstall the original Windows system that was on your computer when you bought it. You don't want to choose this option, unless your computer originally came with Windows 10.

Step 5: You will be presented with the option to Just remove my files or to Remove files and clean the drive. Basically, if you intend to keep the computer for yourself, pick the first option. If you intend to give it away or sell it after the reset, choose the second option, which will take much longer to complete.

After choosing an option, click on the Reset button and that's it. The computer will restart and after somewhere between 10 minutes to half an hour, or maybe longer depending on the speed of the machine, you will have yourself a computer with Windows 10 freshly installed. Note that resetting your machine in this way means you'll lose the option to roll back to the previous Windows.

For Windows 7/8 machines

If your computer still runs Windows 7 or 8, you want to avoid upgrading using Windows Update. Instead make yourself a Windows 10 installation disc. I prefer using a USB flash drive (thumb drive) since it works with all computers, including those without an optical drive. You'll need a drive that's 3GB or larger. Here are the steps.

Step 1: Go to Microsoft's Windows 10 download page and click on Download tool now to get the latest media creation tool.

Step 2: Run the downloaded tool, choose Create installation media for another PC then click Next.

Step 3: In this step, you select the Language, Edition and Architecture for Windows 10, then click Next.

Note that the N version of Windows 10 is for some European countries and will not include Windows Media Player. Read more about these specifications here. If you choose to make the installation media for both 32-and 64-bit Windows, you will need a thumb drive that has at least 6GB of storage space. If you intend to install Windows 10 on the current computer, you can check the Use the recommended options for this computer box.

Step 4: Choose USB flash drive.

Step 5: Insert the flash drive into the computer's USB port and click Next. After the drive is selected the tool will start downloading Windows 10. Depending on the speed of your internet connection, the download can take anywhere from a few minutes to a couple of hours. Once the download is done, the tool will takes another few minutes to turn the flash drive into Windows 10 installation media. You then can use this flash drive to upgrade or install Windows on any computer.

Step 6: Insert the installation media flash drive into a computer running Windows 7 or 8 that you want to upgrade. Open the drive in Explorer and double click on the Setup file. The upgrading process will start.

Step 7: After a short preparation, including checking for updates from the internet and asking you to agree to terms and conditions, you will be greeted with the Ready to Install dialog. Click on Change what to keep.

Step 8: In the next step, you can choose to keep Nothing (so that you'll have a truly fresh Windows 10 install), Keep personal files only (your documents, music, photos and so on will remain intact) or Keep personal files, apps or Windows settings (you will not have a clean installation of Windows 10). After that click Next.

Follow the rest of the installation and once it's done, if you have pick the option to keep nothing or just personal files, you will have yourself a clean installation of Windows 10 on your machine.

For a custom-build computer (advanced users)

If you've built your own computer, you can install Windows 10 on it using the flash-drive creation method in the section above. Choose to boot the computer from the flash drive and the installation process will start. Note that this method is quite involved, though self-explanatory, so make sure you know what you're doing (or are willing to learn a few new things).

Also note that installing Windows 10 fresh on a computer by booting from the installation media will require you to buy a new Windows 10 license. If you do this before July 29, you can use a Windows 7 or 8 license to activate Windows 10.

Good luck!

Update, July 28: Information added to reflect the latest build of Windows 10.