Tom has a five year old Gateway laptop and he's running out of hard drive space. He would like to replace it with a 1TB hard drive and install Windows 10. Leo says that since Tom has Windows 7 on his laptop, he gets a free Windows 10 upgrade. So once he gets invited by Microsoft to install it, he can do that easily.
Leo suggests going to Thurrott.com and look for a tutorial on how to do a clean install of Windows 10 directly with the Windows 10 ISO. Leo doesn't really recommend it, so he should make sure to backup all of his data first. Then he can download the ISO, and that way he'll get installed media for Windows 10. Windows is tied to the machine, so when he makes that change, he'll need to input his Windows install key.