Stall The Ball

From http://windowsvistablog.com/blogs/windowsvista/archive/2008/03/18/windows-vista-sp1-released-to-windows-update.aspx

Those of you, who know me, know I think Vista was a blight on the computing landscape. SP1 does address a lot of the shortcomings of Vista but it still doesn't do it for me.
Wait for SP2 in true Microsoft tradition of getting it right on the third attempt.

If you don't see SP1 update listed in your possible updates it could be because of any one or more of the following.

SYMPTOMS
Windows Vista Service Pack 1 (SP1) is not available for installation from Windows Update, and Automatic Updates does not offer Windows Vista SP1 for installation.

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CAUSE
This problem occurs because of one or more of the following causes.

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.

For more information, visit the following vLite Web site:
http://www.vlite.net (http://www.vlite.net)
Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

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.

See here for the multitude of fixes