For example, on days four through 27, a pop-up asks the user to activate once each day. As the grace period shrinks, however, increasingly-frequent messages appear on the screen. During the 30-day grace period, Windows 7 operates as if it has been activated. Microsoft allows users to install and run any version of Windows 7 for up to 30 days without requiring a product activation key, a 25-character alphanumeric string that proves the copy is legitimate.
