If you open the file browser on Windows XP, you might find a small yellow dog on your screen. His name is Rover, and you can put it anywhere you want!
It barks at you, wanders around and is quite neat.
It is based on the Microsoft Agent SDK and uses the same dog that appears in the find files tool in Windows XP.
Rover's first appearance is in Microsoft Bob, in 1995. However, the software didn't really success, so as a way to salvage this canine, they made him the default assistant.