Though Microsoft's Windows Product Activation already has appeared in other products, the anti-piracy scheme has come under a spotlight with the impending release of Windows XP.

Microsoft has gone to great lengths to explain that product activation and registration are two completely different things. Product registration is voluntary and requires detailed personal information for use by the company's product support and marketing departments. Activation is primarily a copy-protection scheme that prohibits the long-term use of a single licensed copy of the software on multiple machines.

The anti-piracy mechanism comes into play when updating Microsoft software on existing systems. The process creates an installation ID using the product key supplied with the software combined with a hardware "hash" of various hardware components. The hardware identifies 10 elements of a PC's hardware configuration and assigns values that translate into a 50-digit code.

Users give Microsoft that code by Internet message or phone call, but it's virtually impossible to decode the hash value--a numeric value derived from the original data source--to identify a particular machine.

If the product-activation process finds a mismatch, it basically throttles down the operating system to a minimal function level. Microsoft requires activation within 30 days of loading the software, or the anti-piracy feature kicks in.

Product activation won't be an issue with respect to most new PCs purchased with the Microsoft operating system or other Microsoft software already installed. It will also be a nonissue for customers who buy volume licenses--five or more copies--of Windows XP.

The activation agent takes into account that users can change system hardware configurations for component replacement and hardware upgrades: Therefore, users can change six of the 10 components examined by the hashing process without reactivation. That number drops to four if the network interface is one of the components.

More substantial PC hardware upgrades could trigger the need for reactivation, which can be accomplished by contacting Microsoft to acquire another confirmation ID. This also applies if the hard disk needs to be reformatted and the software reinstalled.