1. If you have a valid Windows XP key, connect to Internet and start Windows Update.
2. If you don’t have a valid Windows XP key, look around to find some cheap Windows XP key. I saw that some people sell them with a very cheap price.
3. Here is the easiest way do bypass the latest WGA: Just download the WGA bypass.zip, unpack and run the file MGA_crack.exe. Follow the instruction and you are all done !

Windows 7 user ? Please follow Bypass WGA Windows 7