Follow this simple steps.
1. Click Start Menu, then click run.
2. At RUN, type notepad
3. At Notepad, Hit CTRL + O (file menu>open).
4. Browse for this file
C:\Windows\system32\drivers\etc\hosts5. Below the line of "
127.0.0.1 localhost", add this line "
127.0.0.1 mpa.one.microsoft.com"
6. Now Restart and Run Windows Update.
Don't worry about the WGA, it wont bother you anymore.
or visit this blog: http://rollsroy.blogspot.com/2008/08/how-to-make-your-windows-xp-genuine.html