The IntelliMouse USB offers true "plug and play" functionality and allows you to connect your mouse without having to turn off and reboot your machine. Simply unplug one USB peripheral and plug in another and your PC will automatically recognize the new device and configure the necessary software.  

The IntelliMouse USB also offers the enhanced functionality of the PS2/Serial IntelliMouse including zooming, data zooming and universal scrolling.  
 
Benefits  
Work more comfortably using the ergonomic shape and natural alignment of IntelliMouse. 
Scroll smoothly and precisely through screens of information with a simple roll of the wheel. 
Work hands-free with Auto-Scroll. Press the wheel, set the scroll speed, then watch your document scroll automatically. 
Zoom quickly. in or out by holding the CTRL key while rolling the wheel (in Office 97 - compatible applications). 
Feel the comfort of Microsoft IntelliMouse. Its raised back fits the palm of your hand, and its side is curved so its easy to hold - whether you're right-handed or left-handed. 
Count on the Microsoft guarantee. If you're not satisfied with your mouse for any reason, return it within 30 days of purchase for a full refund.