Please refer to the steps below to disable the touchpad when a USB mouse is installed:
1. Turn on the VAIO computer. When the Sony logo appears, press F2.
2. Highlight the Advanced option using the arrow keys, select TouchPad/Ext.PS/2 Mouse and press Enter.
3. Select the Disable Both option.
* The option is set to Simultaneous> by default.
4. Press Esc twice. Select Exit (Save Changes) and press Enter twice.