Ad first you have to check if the /device-drivers/usb/hdi-support in your kernel is activated, put I suppose it is if you'r using the standard kernel. Then you have to edit the /etc/X11/xorg.conf (for xorg, xfree has another name). There has to be something like
Section "Input Device"
Option "Protcol" "auto"
Option "Device" "/dev/..."
Option "ZAxisMapping" "4 5"
Normally if you set Device to /dev/input/mice tochpad and usb mouse should work. If they do not, you have to take a look at the /dev/input devices with
There should be several devices
try [HTML]cat /dev/input/mice0 (and so on)[/HTML]
now move your mouse, you should see many strange symols, wenn you have found the right device, then abort with contrl+c and enter this device in your xorg.conf.
P.S. the last option enables the scroll-wheel