Rick upgraded Windows 10 on a secondary drive, keeping Windows 7 on his C drive. Now he has a dual boot option. However, with Windows 7 support going away, how can he make sure he's OK if he has to replace that secondary drive? Leo says it'll authenticate automatically because Microsoft gives an entitlement based on the entire machine, not a hard drive. If he had to replace the motherboard, video card and hard drive, then he'd have an issue. But changing a hard drive won't cause the problems. When he replaces the hard drive, just use the Windows Media Creation Tool to create an "install" USB key (16GB or better) and then he can just run it by booting to the USB key. Run setup and Bob's your uncle.