I've got two mouse devices, a PS/2 touchpad and a USB Logitech mouse which I use interchangeablty. With Win 2000 and WinXP both devices installed correctly and I can use one or the other at will. With Win98 or ME, it will not complete startup once the VIA USB drivers have been installed. Booting halts before the GUI comes up and the system often reboots by itself. To boot successfully I must disconnect the USB Mouse . The USB appears to install correctly, no warnings in Device Manager. I have not tried just the USB mouse without the PS/2 device.