If you put your computer into hibernation, the next time you turn it on, you'll get all your windows and programs open just the way they were before the shutdown.
In this day of age, it's very practical to have a Windows 7 installation on your USB key, for many netbooks and devices don't come with CD/DVD drives anymore.
You have more people using one computer and you don't want them to be able to shut it down using a shutdown button on Windows logon screen, this is how you remove it.
Windows Explorer does not have menu displayed by default like you were used to in previous versions. To activate and keep it permanently visible follow this tutorial.