Simplest thing to do is to take your old mouse with you to make sure you get an identical type of plug.
However - when I bought my system a few years ago I was supplied with a trackball by mistake (instead of a mouse). I decided to try it anyway and quite honestly for me it's miles ahead of using a mouse. For a start my space is limited so it sits stationary on a small pad (with gel wrist support) and the only difference is that the ball is on top rather than underneath. It also has wheel similar to the MS Intellimouse. It took a while to get used to it - all of about a minute. I've worn this one out - my contact is getting me another one tomorrow.
Suggest you go to your nearest computer shop and ask to try one out.
[ 27 January 2002: Message edited by: FJJP ]</p>