I recently had a Vista installation which gave me an error on every update I tried, namely 80071a91. Googleing 'round brought me to http://blog.stevex.net/index.php/2007/05/21/80071a91/. I tried the suggested solution, finding that the delete statements didn't work: The files were in use by another process. That was quickly solved with a tool from http://www.creativelement.com/ and a reboot. Now I was able to continue the solution method and regain access to Windows updates on this Vista machine.
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