If WGA determines that a user's copy of Windows is unauthorized but was installed from seemingly-legitimate media (i.e., the CD and holographic emblem present on real copies of Windows seems genuine), then Microsoft will supply the user with a new CD.
Microsoft has indicated that they will continue to deliver critical security updates through their Automatic Updates service as well as via the Microsoft Download Center, so that all systems, including those that fail to pass validation, will still continue to receive critical security updates.
The company has made installation of Windows Genuine Advantage a requirement for use of the Windows Update and Microsoft Update websites, in part to be sure that customers who use support resources of the company are aware when their software is unlicensed.
Even if WGA does not really make the program unusable, no updates except critical ones can be downloaded from Microsoft.
Rather than just disallowing updating, Windows Vista originally ran in reduced-functionality mode if found by WGA to be compromised if a product has not been considered genuine which has made some people compare WGA to time bomb software.
As of July 2006, the latest update blocks management by other means.
The program uses either a stand-alone program to generate a key or an Active X control to discover whether the license key is valid; either way an Internet connection is required.
It does not cover other versions of the Windows NT family, such as Windows 2000, Windows Server 2003 and Windows XP Professional x64 Edition, or the Windows 9x family.
The Active X control however checks Windows 2000 Professional licenses as well.
Microsoft has also provided removal instructions for the pilot version of WGA.