What does this mean exactly? Well, if you have your system set to automatically receive the windows updates, then you will most likely not receive this, however if you have ever performed the windows updates yourself, and/or have experienced with an earlier 'beta' release, then you may already have xp sp3 which will essentially have to be uninstalled before the automatic update will take place, whenever that may be. If you haven't experienced any problems with the earlier releases then do nothing for now, and once it is a public release, I would suggest uninstalling the beta at that point. The fact is, if you haven't had any troubles, then you are probably witnessing an increase in performance if nothing else, as this is most definitely what I noticed with the pre-release versions.
