Microsoft has begun distributing Windows Vista Service Pack 1 as an automatic update.

The move will allow users who have not already downloaded the service pack to obtain it automatically.

Vista Service Pack 1 promises improved performance and stability, along with a cumulative security update.

A company spokesperson told vnunet.com that the update is being distributed in several smaller downloads. Users should wait until all the packages have been downloaded before expecting the update to run.

The SP1 update was released to PC manufacturers in early February, and was made available as a voluntary download in March.

Microsoft shipped the third service pack for Windows XP to manufacturers on 22 April.

The company plans to stop allowing manufacturers and vendors to offer XP for all but the lowest-end PC models in late June.