Kensington Optial Trackball Mouse
This is the Kensington Expert Mouse Pro. I first purchased one of these in 2004 and ever since has been a huge fan of the Kensington range of trackball mice. The trackball has several buttons that can be each program to open a website of your choice. It also has four large buttons that can each be programmed to call various controls such as click, double-click, drag function, and right click. You can program the mouse to have these controls on any particular button you like. As far as I am aware this trackball is no longer available for purchase so if you have got one and are still using it on XP, I would look after it very carefully.
Unfortunately this product doesn't seem to be available anymore
This is the Kensington Expert Trackball Mouse. This is the successor to the Kensington Expert Mouse Pro. The expert trackball mouse is optical which means it uses light to sense the movement of the ball. The advantage of this type of mouse is that dirt will not inhibit its performance, unlike the expert mouse pro which used mechanical sensors, if any dirt found its way on to the sensors the mouse would not work properly. Whereas this mouse doesn't possess any launch buttons I find this doesn't really detract from its functionality. There is now a rotating ring around the ball that you can use to scroll up and down the page. The mouse is a slightly different shape and might take a little bit of getting used to. The build quality seems a little more superior than the expert pro trackball and I much prefer the look and colour of it.
The software that came with the Kensington Optical Trackball mouse does not work on Vista 64-bit and Windows 7. However, there is now some software available called "trackball works" that you can install onto your PC which will then enable you to program your mouse so you can use all the functions that are built into this fantastic product. Please click here to download Trackballworks. Once it downloaded onto your PC, extract the files onto your desktop and basically follow the instructions. You can purchase a Kensington Optical Expert Trackball Mouse from Amazon.co.uk