USB optical wheel mouse not detected by XP
You can try to:
Right click on "My Computer", click on Properties, click on the Hardware tab, click on the Device Manager Button, expand your Mice and other pointing devices. verify that you 2 entries. One is the Sony builtin (Alps in my Vaio) and a HID-compliant mouse. The latter is your external optical wheel mouse. Make sure it does not have any red or yellow mark. Double click on the HID and verify that the next window says "This device is working properly." If not follow on screen instructions to enable or activate.
Hope this be of some help. Good luck and pls post again how things turn up or if you need further information.