A friend of my had pirated version of Windows Vista; and he wanted to get Windows 7. Since he is student as me; he can download licensed Windows 7 legally from college. So he did, and installed it. From Windows 7 side, everything was ok. But when he booted back to Windows Vista; he had a notification that his Windows have been detected not to be genuine and to input serial key; or something like that. Since he is happy with Windows 7; he got rid of XP and copied files from Windows 7
My question is purely academic; how is it possible for Windows 7 to modify Vista partition? And, yes, Windows 7 was installed to separate partition.