Installing Windows Vista SP1: Before You Begin

From the installation notes:

Before you begin

Before you install SP1, do the following:

• Make sure your computer is running Windows Vista.
• If your computer is running on battery power, plug it in so that your computer does not lose power during the installation.
• Close any open files and programs before installing SP1.
• If you are downloading SP1, select the 32-bit SP1 if you are running a 32-bit edition of Windows Vista. Select the 64-bit SP1 if you are running a 64-bit edition of Windows Vista. To find out which edition you are running, click Start, right-click Computer, and then click Properties. In the System section, you can view the operating system under System type. If you are installing SP1 from an installation disc, the correct version will install automatically.
• Make sure there is enough free space on your computer's hard disk to install the service pack. The 32-bit SP1 requires a minimum of 7 gigabytes (GB) of free space; the 64-bit SP1 requires a minimum of 13 GB of free space.
• Back up your files to an external hard disk, DVD or CD, USB flash drive, or network folder.
• If the configuration of your antivirus software prevents certain system files from being changed, SP1 installation might fail. Try temporarily disabling your antivirus software. You can usually do this by right-clicking your antivirus icon (which typically appears in the bottom right-hand corner of the computer screen) and clicking Disable. If you disable your antivirus software before you install the service pack, be sure that you are aware of the risks involved, and be sure to enable it after the service pack is installed.