The shutdown process is one of the aspects of the Windows operating system that evolved from XP to Vista. In this context, Microsoft emphasized even before the consumer launch of Vista that the power management sub-system of the operating system had been extensively overhauled. The immediate results are faster shutdown times and the reliability of the shutdown system. In Windows XP neither functioned properly. XP always managed to take its due time before turning off, that is when the switch off process actually finished and didn't hang. This has all changed in Vista. Microsoft claims that its latest Windows platform will shut down faster, but also that it will no longer be influenced by any applications that fail to close simultaneously with the operating system.
"One of the most significant pieces of feedback that we received about Windows XP was that people (especially people with laptops) were quite upset at the amount of time that it took for XP to shutdown. The big reason for this was that XP didn't reliably shut down the system. On Windows XP, an application was allowed to delay system shutdown indefinitely - this was a major cause of the overheated laptop problem; on Vista, the system IS going to shut down, even if your application isn't ready for it. So if your application takes a long time to exit (and Microsoft applications are absolutely NOT excluded from this list), than it's going to have the rug yanked out from under its feet," revealed Larry Osterman, Microsoft Software Design Engineer.
In addition to Shutdown, Restart, Switch User, Lock and Log Off, Windows Vista comes with an optimized Sleep option. Sleep will save the current state into RAM allowing users to quickly resume their session. In Vista, the default turn off option is actually Sleep and not Shutdown. "The Windows shutdown process is: shutdown all the users' applications; play the shutdown sound from the shell and stop the shell. If the system is in "forced shutdown" mode, than 30 seconds after the prompt, the system WILL kill the remaining applications, regardless of whether or not they're shut down," Osterman added.
Microsoft, Windows Vista, Shutdown, Vista Shutdown