The updates install files not in use and then wait until a reboot to replace
files in use. The files are actually replaced when the system first boots up
but before the files are put back in use again.
IF one installs an update for a security vulnerability and there is a file
in use that requires replacement because of said sec vuln, then the system is
still at risk until it's rebooted.
So, in essence, the installation of updates is not dependent upon the system
being shutdown to get the files installed rather, it's the restarting of the
system and the 'release' of a file or files in use that the installation of
the update is dependent on.
MowGreen [MVP 2003-2008]
> Finalizing a windows update should not have to restart the system, i think
> you should figure out a way to install the updates and then not have to
> restart, and the important updates should install when you boot up, not when
> you shut down.
> This post is a suggestion for Microsoft, and Microsoft responds to the
> suggestions with the most votes. To vote for this suggestion, click the "I
> Agree" button in the message pane. If you do not see the button, follow this
> link to open the suggestion in the Microsoft Web-based Newsreader and then
> click "I Agree" in the message pane.