Windows Product Activation

Windows Product Activation (WPA) is a system utility introduced in Windows XP. It is implemented in the OOBE application. It was introduced to prevent piracy, but was very controversial at the time.

Windows XP
The first build to have Windows Product Activation is Windows XP build 2410, but it was non-functional until build 2428, where it prevents login after 14 days; however, it still can be deactivated over the registry, and Safe mode bypasses it as well. It received its final appearance in build 2465. Windows XP build 2542 extends the grace period to 30 days, although it has been reverted to 14 days in Windows Longhorn build 3683.

Longhorn

 * Main article: Windows Longhorn build 4093 (main)

It was rewritten as an Avalon-based application in Windows Longhorn build 4093, but it is largely incomplete. It is included as  in the .NET Framework library folder, and thus being completely detached from the non-functional OOBE. Previously, Windows Product Activation was not available in componentized builds of Longhorn.

Functionality
Windows Product Activation can be invoked by launching  with the   parameter. It offers activation over the internet (which no longer works, as the servers have been shut down) and over telephone (which still works as of 2022), as well as registration at Microsoft. The user can also activate Windows in the OOBE.