Did you try the steps in the following KB:
WINUP: "Software Update Incomplete, This Windows Update Software Did Not
Update Successfully" Error Message When You Visit the Windows Update Web
Site
http://support.microsoft.com/default...b;en-us;319585
--
Thanks,
Lucy [MSFT]
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<> wrote in message
news:e36401c3f076$04c51d60$...
> While trying to update my system, I always get the
> Message "Software Update Incomplete, This Windows Update
> Software Did Not Update Successfully".
> None of the tips & tricks described in the Knowledgebase
> articles worked.
>
> My system is XP prof, SP1. I'm logged into a Domain,
> Server is NT4. I have administrative rights for the domain
> and locally.
>
> When I log in as a local administrator, I'm able to
> update, however when I try it again with my normal user
> account, it will not work.