The WGA tool is used to curb Windows piracy and consists of two major components: validation and notification. Validation determines whether the copy of Windows installed is pirated and Notification nags users when Microsoft believes you are using a pirated version of the operating system.
The problem is that Notifications has been "phoning home" to Microsoft server every day and Windows users are concerned about how it violates their privacy and security. To prevent the transfer of information, the private security company created the utility, RemoveWGA, which works on Windows XP (SP1 and SP2).
The utility can be downloaded here but it is not intended to be used to run on pirated versions of Windows. You should only use the tool for preventing the violation of your privacy and security if you have a genuine version of XP. I would never condone software piracy.