Yes Kemical is right, the preferred way is to install any service packs after a clean install of an OS. I myself installed it through windows updates when it was made available. I have yet to see any adverse effects from the update. I bought my PC back in late February of 08 and service pack 1 was released shortly after my purchase. So I did not have my system for a year and then updated service pack. As we remembered downloading sp 1, 2, and 3 for xp, thats exactly how most of us installed those service packs after having it for a year or more, right from the auto update center. Most of us if not all of us had no ill effects from doing so. In my opinion it's worth downloading vista's sp1, it helps fix some known issues and vulnerabilities that exist. Just like MS is working on sp2 for more of the same. So what ever you decide post back with results....good luck.