You need to go to the manufacturers website (of your mouse) and download the latest drivers from there.
To uninstall the existing drivers (or software):
For mouse software (for example Logitech use 'SetPoint'), go to Control Panel > Add/Remove Progams and find it in the list.
For mouse drivers go to Windows Explorer, right-click on My Computer and select properties; go to the Hardware tab and click on the 'Device Manager'. That should provide you a list of all the devices on your PC. Go down to 'Mice and other pointing devices' and you mouse should be listed under there - right click on it and select uninstall.
To reinstall the mouse:
Windows XP should actually automatically detect it. Plug it into the USB port and see what happens - if it chimes and then comes up with the dialogue box saying that new hardware is found, you may be able to install it automatically. If not, use the driver you downloaded from the web.
If that doesn't work:
If neither methods work, it may actually be your MoBo's USB drivers. If this is the case you might have a problem, as Brandname PC's (ie. HP, Compaq, Dell, etc) are very specific. You might be able to go to the PC manufacturers website and go to Help & Support.... let me know if that is the case...
Hope that helped!!??!