Windows Vista SP1 enables support for hotpatching, a
reboot-reduction servicing technology designed to maximize uptime.
It works by allowing Windows components to be updated (or
patched) while they are still in use by a running process.
Hotpatch-enabled update packages are installed via the same methods
as traditional update packages, and will not trigger a system
reboot.
Other changes:
Improves patch deployment by retrying failed updates in cases where
multiple updates are pending and the failure of one update causes
other updates to fail as well.
Enables reliable OS installation by optimizing OS
installers so that they are run only when required during patch
installation. Fewer installers operating results in fewer points of
potential failure during installation, which leads to more robust
and reliable installation.
Improves overall install time for updates by optimizing the
query for installed OS updates.
Improves robustness during the patch installation by being
resilient to transient errors such as sharing violations or access
violations.
Improves robustness of transient failures during the disk cleanup
of old OS files after install.
Improves the uninstallation experience for OS updates by improving
the uninstallation routines in custom OS installation code.
Improves reliability of OS updates by making them more resilient to
unexpected interruptions, such as power failure
Source: ActiveWin
I bet mine would be a failure if i were to game 
