Please refer to the steps below when you only want to use MSAC-US5 mouse:
1. Double click [Sony USB Mouse] from [Add/Remove Programs Properties].
2. Select [Yes] on the [Uninstaller] dialog box.
3. Connect the USB mouse and USB connector. You can then use the other USB mouse that uses Microsoft original USB mouse driver.
You have to restart the PC after installing the driver. Otherwise you might not able to use the wheel function.
Alternatively, you can download the updating program [Sony USB Mouse Driver 1.41 Update Program] from the VAIO FAQ support web page and update to the new driver.