Windows Product Activation (WPA) is Microsoft’s way of keeping you from installing a copy of Windows Vista on more than one computer. It basically marries the copy of Windows Vista you’ve purchased to the computer’s hardware it’s installed on.

The WPA Process

When you enter the product key three identifiers are generated and collected:

• Hardware ID: A unique identifier that’s generated from information gathered about the computer’s hardware.
• Product ID: A 25-character unique key supplied when you purchase Windows Vista.
• Installation ID: An identifier Windows Vista creates from the hardware ID and product ID.

During the WPA process the product and hardware IDs are sent to Microsoft and the computer is “activated”.

If you make significant hardware changes (like replacing the motherboard and graphics card at the same time) you’ll have to re-activate your copy of Windows Vista.

Note: You don’t have to activate Windows Vista during the first 30 days of use.

If you’re installing Windows Vista I highly suggest not choosing to automatically activate Windows Vista during the installation. You should wait the full 30 days to make sure all of the hardware is properly working before activating.