Unlike the mechanical-trackball "mice of yore" that skip, stick, and need to be cleaned, the Microsoft D68-00007 TrackBall Explorer introduces an entirely new trackball featuring optical sensor technology. Reading through dirt, dust, and fingerprints, the optical sensor tracks the movement of the ball 1,500 times per second, giving you smooth, precise control. The Trackball Explorer comes with two additional buttons located on the side of the device--for a total of five buttons--for moving forward and back quickly in your browser, or you can program them. It also features a wheel for efficient scrolling and zooming and is ergonomically designed to support the natural position of your hand as you use your index finger to control the trackball. Product Description MODEL- D68-00007 VENDOR- MICROSOFT CORPORATION FEATURES- TrackBall Explorer- PS/2 & USB The TrackBall Explorer sets a new standard in trackballs by combining an IntelliEye optical sensor and an advanced ball design. The IntelliEye optical sensor tracks the movement of the ball 1500 times per second to give you unbelievably smooth precise control. * IntelliEye optical technology for more precise and better control than an old-fashioned mouse with a ball. * Browse easily with the programmable forward and back buttons. Scroll efficiently with the wheel. * The shape supports your hand in a natural posture. The ball is positioned for fingertip control and easy navigation. * The IntelliEye sensor has no moving parts to clean so your trackball stays smooth and precise. REQUIRES- 29MB of available hard-disk space CD-ROM drive Round mouse port (PS/2 compatible) or USB port (USB requires Windows 98 or 2000) Windows 95/98/Me/NT Workstation 4.0 with Service Pack 3 or later or Windows 2000. IntelliPoint software (included). MANUFACTURER WARRANTY: 3 YEARS