This was a new feature added to Windows 7. You can dock images onto three different spots on the screen and they will resize: You can dock the window to the top so it will maximize fully or you can dock them left or right to the screen to make them tile vertically in the middle of the screen.
To do this just grab a window and move it all the way to the top/left/right and let the mouse go again. Making working a lot easier and faster!
It is basically the same as in Vista but this time Windows 7 has a GUI for it to make things easier and for a higher level of control.
Press WindowsKey + R (or go to Start->Run) and type in "msconfig" (without quotes). Hit Enter.
Go to the Tools Tab, choose "Change UAC Settings" and hit Start.
A new GUI will open. Slide the slider all the way down to disable UAC completely and hit OK.