If you need to close multiple applications and windows at once, then it will definitely be time consuming. Try Close All Windows, it is a light-weight tool which closes all open windows simultaneously with a single click.
This tool was originally developed back in 2006 for Windows XP only. But why not give it a shot on Windows 7 as well? This tool has no interface, just run it and it will close all windows instantly. To make things easier, pin it to the Windows 7 Taskbar. A simple click and it closes all windows without any problems.
It works on Windows XP, Windows Vista, and has been tested on Windows 7 too. If you need a more advanced tool, try out SmartClose, which closes and restores applications and works great on Windows 7 as well. Enjoy!