What's big and red and glows when you touch it? Two burly new Microsoft Trackball mice: Trackball Optical and Trackball Explorer, scheduled to be available in October. Unlike a standard mouse, which uses a ball and rollers to track movements, these mice implement Microsoft's IntelliEye technology. IntelliEye uses a digital signal processor to take 1,500 digital snapshots per second of the surface on which you're mousing. Then the digital signal processor tracks the changes between images and translates them to movements on the screen. The thumb-controlled Trackball Optical features five buttons, two of which are customizable function buttons, and a scrolling wheel in the middle. Although the sleek plastic design provides an ergonomically pleasing place to rest your hand, the device itself takes up twice the amount of space that a standard size mouse does. It costs around £28. With the other new device, the Trackball Explorer (around £40), you use your index finger to control movement. This mouse features a scrolling wheel and the same five customizable buttons. One problem with the configuration of this mouse, however, is that the buttons tend to confuse the fingers -- you'll need to click with your seldom-used pinkie and ring fingers, while the Optical mouse lets you click the main buttons with your index and middle fingers. Both Trackball Optical and Trackball Explorer connect directly to either a USB (if you're using Windows 98, 2000 or a Mac) or PS/2 port. IntelliPoint software for Windows and Macintosh is included with both devices. If you have a Mac, you need to be running Mac OS 8.5.1 or later, and iMacs require iMac update 1.1. Alas, if you're a lefty, like Microsoft chairman and chief software architect Bill Gates, you won't be able to wrap your hands around one of these glowing mice, since these models come configured only for right-handed mousers. If your heart and your left hand is set on a glowing red mouse, Microsoft's previous IntelliMouse Optical is your only ambidextrous option.