I have read the topic you referred.
Here I just want to say that you cannot keep your Windows up-to-date for a long time if you are using a pirated copy. To bypass such checks while downloading an update is very easy. Because, such checks are optional. Moreover, I am also helping you to keep yourself up-to-date, even if you are using a pirated copy.
Click here to know how. But, when a major update is released - like SPs that contains an in-built validation checker - you cannot really bypass it. Well, you can use keygen to install XPSP1, but you have to reinstall XP using another keygen for loading XPSP2 and finally when you would load XPSP3 you have to format your previous installation. Is this really a good solution? The tool discussed on that topic just generates a key of XP pattern, which has not yet been detected as a pirated one. But, it is not much difficult to make this tool invalid in SP3. So, there is nothing to worry about.