iOS 8 for example takes up 5 Gigabytes, Windows 10 x64 is 11 Gigabytes.
Note: It was a blessing and a curse. He was a Windows XP holdover despite security issues and his preference for security. He wouldn't transition. The reason? He invested too much time into his XP box to give it up. Plus, looking at the Win7 default install, he figured it would be less fun next time.