I'm running XP and I believe all of my drivers are up-to-date. I was using a Logitech trackball mouse w/serial connection. I disconnected the trackball, uninstalled the Logitech software and cleaned my registry. I then connected a new Micro$oft optical trackball w/USB connection. I then installed the new software. I got the popup balloon (new hardware detected). The window open for me to install the software. Then I get a popup balloon saying software insalled successfully but cannot locate hardware...your hardware may not work properly. No kidding--it doesn't work at all. I then uninstalled everything again, including clearing the Device Manager. Used "Add Hardware" and tried Micro$oft's own generic mouse drivers to detect its' own Optical Trackball Mouse and it still didn't work! Now everytime I boot, I get a popup and window saying that Windows has found new hardware (mouse). Yes, I've tried using this proceedure...still doesn't work! Hope someone has a fix and/or suggestion...THX BTW...haven't tried Micro$oft support because I've heard "...try reinstalling Windows" one too many times. :disgust: