If you are having issues with the free upgrade to Windows 10 - or if you want to perform a fresh install to a freshly formatted hard-drive - then the Windows 10 ISO Tool is what you need.
A physical backup
The site the download link redirects you to hosts both 32-bit and 64-bit versions of Windows 10. To use it you will either need a DVD burner or a USB pen-drive with enough space to store the file, this can then be used to perform a fresh install of Microsoft's new OS. But, keep in mind, you will need a valid serial number from either Windows 7 or 8 to install it.
Everything you need
The linked files include; a file format optimized for speedy download, media creation options for USB and DVDs, and the ability to convert the file to an ISO format. This page also outlines system requirements and redirects to a full explanation of the installation process.
Only if the free upgrade option has failed you
Windows 10 ISO Tool is useful if you are having problems with the Windows 10 free upgrade install. It is, however, more complicated than the automatic option so is only really for experienced users or those who experience installation problems.
You can see our full review of Windows 10 on the site, where you can find out more about the free upgrade options for Windows 7 and 8 users.