The change runs counter to previous practice by the Redmond, Wash. developer. With Windows 7, for example, users could run the OS for 30 days before activating the copy by providing a legitimate key.

That "grace period" was used by some to evaluate the software , to by using an "upgrade" license to install the OS on a newly-formatted hard drive, and to create physical partitions or virtual machines for quick testing purposes.

Because Windows 8 handles activation differently, the grace period has been eliminated.

As blogs , customers must enter a unique product key -- a 25-character alpha-numeric string -- to proceed during Windows 8 setup. Failure to do so stops the process in its tracks. The Consumer Preview and too, although Microsoft provided users a generic key for those sneak peeks.

Once Windows 8 is installed -- assuming the machine is connected to the Internet -- it automatically seeks out a Microsoft server to verify that the key is valid and then activates the OS. "If the licensed computer is connected to the Internet, the software will automatically connect to Microsoft for activation," states the end-user licensing agreement, or EULA, for Windows 8 Pro.