If on your Windows 7 computer opening programs, saving documents, browsing the Internet and other every day tasks are getting slower, this is how you speed up things without installing an additional program.
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.
If you leave your computer running on a 24/7 basis you might be interested in determining the amount of uptime that has accumulated since the last reboot.
Windows 7 have a nifty feature which combines the windows of opened applications under the same taskbar button. If you don't like it you can always turn it off.