Re. both your re-install comments....my thoughts precisely
Yes, the laptop is fine.
While checking Event Viewer for this update problem, I also checked for anything else which may have caused it. I checked from September 2009 when it was purchased, but there's nothing significant in the System or Application section. I've also done AV and Malware scans just in case.
Then try installing it from the download link (download it to the desktop first)
Even though that link isn't specifically listed for Vista ?
Re. the function of .NET Framework....since this problem occurred my relation has downloaded Avira, CCleaner, other Vista updates, Malwarebytes and Belarc with no problems but perhaps these are not associated with .NET Framework ?