WGA stands for Windows Genuine Advantage. Microsoft Corp. uses the Windows Genuine Advantage program to help in its fight against piracy of its Windows operating systems, particularly Windows XP and Windows Vista. It is delivered to a user's computer through the Windows Update service (usually through Automatic Updates, which is switched on by default and works mostly in the background with little user interaction).
For Windows XP users, a WGA check is mandatory to download software items such as Windows Media Player updates or DirectX. When a user tries to download software using the Internet Explorer web browser, they are prompted to validate their Windows installation. If the installation passes, then the user can go ahead and download the software, but if it doesn't, the software item is not available to the user. The program alerts the user about the legitimacy of the installed software and gives information on what to do. It also flashes reminders regularly from then on.
For Windows Vista users, much of the same limitations enforced by WGA on XP users apply, although some more severe limitations are enforced for Vista. Pirated copies of Vista will have some of Vista's new advanced features such as Aero disabled.
WGA has come under fire for many reasons, not least of which is its false positive results. Many Windows users have reported being told they are not using genuine software even though they are. This happens for many reasons and Microsoft has opened a support forum for legitimate customer caught in the mess. Additionally, a recent update to the program added a "Not Sure" answer.
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