Ouvrez le menu Démarrer and then Ctrl+Shift+Faites un clic droit sur in any blank space above, around or on the "Shutdown" button will bring up an option to "Exit Explorer" as shown:
À l'origine, j'ai found this on HowToGeek and have used it in Vista for the last year. It results in a much more graceful closure of Explorer without actually logging you out.
You will still need to open Gestionnaire des tâches afin de launch Explorer again though, Alex's answer details how vous pouvez quickly bring up the Gestionnaire des tâches to relaunch Explorer.
The same can be done on Windows 8 by doing the same action on la barre des tâches instead (thanks to Karl in the comments). This is presumably as the Start button is now missing.