If you want to get the benefit of a year's worth of improvements right now, click the Start Menu, All Programs, and select Windows Update.
Below are reasons why you might not see Service Pack 1 on Windows Update:
Cause 1
You are already running Windows Vista SP1.
Cause 2
Windows Vista SP1 has not been released for the language of the language pack that you have installed.
Cause 3
Windows Service Pack Blocker Tool is used to block the delivery of Windows Vista SP1 from Automatic Updates or from Windows Update.
Cause 4
You tried to install Windows Vista SP1, and the installation failed with a known inconsistency in the file or registry structure.
Cause 5
A hardware device driver or device software was problematic when you updated to Windows Vista SP1.
The Windows Update service can detect the small set of device drivers and software that falls into this category. The Windows Update service will not offer Windows Vista SP1 until an update for the hardware device driver or the device software has been installed.
Cause 6
You have installed a prerelease version of Windows Vista SP1, and you must uninstall the prerelease version, or start with a new installation of Windows Vista.
Cause 7
You used the third-party program vLite to configure the system, and you may have removed required system components that have to be available for Windows Vista SP1 to be installed.
Cause 8
You see one or more updates for Windows Vista when you run Windows Update. However, you do not see Windows Vista SP1 listed.
Download Windows Vista Service Pack 1 (435 MB)
