Windows Genuine Advantage (WGA) program is part of the commitment by Microsoft to protect its customers and partners from counterfeiters through education, engineering, and enforcement of policies and laws. WGA differentiates the value of genuine Windows software from counterfeit software. This enables you to enjoy the capabilities that you expect, the confidence that your software is authentic, and the ongoing system improvements that help you do more with your personal computer.
The WGA program creates an improved Windows experience for users who have a genuine copy of Windows. By using genuine Microsoft software, you can be confident that you will have access to the latest features, security, and support. This helps improve your productivity and expand the capabilities of your computer. You will also have access to innovations and offerings available only to genuine Microsoft software customers.
Windows XP instructions
Run AntiWAT.cmd and wait till it finishes.
Run xpgen.reg and add it to registry.