This is just FYI, based on what I observed & gathered from installing Vista SP1 on several machines today, both desktops and laptops.
1. Before you download Vista SP1, you should first read Windows Vista TechCenter notices, more particularly do if you have problematic drivers.
2. Vista SP1 can be download HERE. Be aware that the file size is 435.5 MB. If your PC is a standalone, you will be better off getting it through Automatic Windows Update. In this case the size of the file you will get is roughly 66 to 69MB, far less than the 435.5 MB.
3. If you find that Vista SP1 is not available for installation from Windows Update and is not offered by Automatic Updates, check out this M$ Article 948343.
4. If for some reason Vista SP1 fails to install, read this M$ article 947366. This article explain what you should and can do.
5. Once Vista is successfully installed, you may be surprised on how much disk space it will take up - nearly 1GB. If you are absolutely certain that there will be no need to ever uninstall Vista SP1, consider using Vista SP1 cleanup tool mentioned in this by Cobra R.
6. Lastly for trivia purpose, Vista SP1 is a cumulative update that consolidated 572 hotfixes and security updates, counted from THIS M$ Technet article.
i_Xp/VistaUser