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.
Virtual Hard Disk or VHD acts like a normal hard drive built into your computer. Cool thing is, it comes in a form of a single file so you can make a copy of it and virtually attach it to any other Windows computer.
A less known but very useful feature that works since Windows XP has been released. You can easily rename a bunch of files in a matter of seconds, let me show you how.