Kensington Expert Mouse Trackball "adapter ps2 serial" Questions

PS2 trackball that I would like to use on a USB Mac. I've tried a commercial adapter that claims to let me use serial input devices with a USB computer, but no results. Is there a driver I need, or is

...adapter to convert my keyboard to USB? I would like to keep this keyboard if possible, since it seems to be ok. Also if I gave you the model and/or serial numbers for this PC, would you be able to ...

...PS2 keyboard adapter, but that did not solve the problem either. The problem is with the keyboard or the computer. Plug the keyboard into a different computer and see if you get the same result. If ...