You may find that your computer updates to Windows 10 even if you don't really want it to.
Microsoft is keen to increase the adoption of it's latest operating system. It has announced that Windows 10 will become a 'recommended update' next year. This means that it will be installed on any Windows 7 or 8 computer with automatic updates turned on (which is the default for most users). Windows 10 will be automatically downloaded and you will then be prompted to install it.
If you don't want to install Windows 10 you do have the option to say 'No' but you will have to look out for this. It is very easy to click 'Yes' to a prompt without properly reading what it says and as a result unwittingly start the installation of Windows 10.
In fact the Windows 10 installation files may have downloaded to your computer without you realising it. It has emerged that Microsoft has set machines to download these files in the background without the user being aware. This has annoyed some users as the downloaded files are between 3-6GB in size. This can take a large chunk out of your broadband allowance and also use up a large chunk of your hard drive (check for a hidden folder called '$Windows.~BT' in your C: drive). Microsoft has since said that this was a mistake and has changed the settings. If you want to reclaim valuable hard drive space it is possible to remove these files by following these instructions.
To prevent the install of Windows 10 you could turn off Windows Update altogether. However this is a bad idea as it means you won't download any security updates which will leave your computer vulnerable to security flaws. We don't recommend that you do this but there are other options.
If you want to know whether it's worth upgrading to Windows 10 read our review: Should you upgrade to Windows 10?
See also Lewis's personal experience of upgrading to Windows 10.