What to do if the touchpad does not work properly, works without touching it, works intermittently or erratically, or is completely unresponsive?

IMPORTANT: 

If the touchpad works intermittently, erratically, or without touching it, the issue may be caused by a recently installed piece of software. Troubleshoot the computer to see if the software is causing the issue.
NOTES: 

This issue may be caused by an installed printer that is not physically attached and turned on. Attach and turn on the printer and then start the notebook. If this solves the issue, contact the manufacturer of your printer for additional troubleshooting information.
Because each of these steps represents a possible solution to this problem, check the touchpad status after completing each step.
1. Make sure that an external USB mouse is not connected to the notebook.
2. Verify the correct AC adapter is being used and connected properly.
3. If the issue is that the pointer is moving around the screen erratically, make sure the touchpad is not accidentally being touched while using the keyboard.
NOTE: Try covering the touchpad with a piece of cardboard or paper while typing on the keyboard to see if in fact the touchpad is being touched while typing.

4. If the issue is that the pointer is moving too fast or that it is difficult to double-tap or double-click, slow down the speed of the pointer and the double-click speed.
5. Turn off and then restart the computer and, as the computer is restarting, press the F10 key to launch the VAIO Recovery application. If the touchpad does not work properly while in the VAIO Recovery application, then the issue might be related to hardware and service maybe required to resolve the issue. If the touchpad works properly, proceed with the rest of this procedure.
NOTE: Unless you wish to do so, or as a last resort to resolve this issue, it will not be necessary to proceed with any of the recovery procedures.

6. Exit the VAIO Recovery application and restart the computer in Safe Mode with Networking.
NOTE: The remaining step of this procedure will be performed with the computer in the Safe Mode with Networking mode.

7. Reinstall the touchpad drivers.
8. Use the System Restore feature to restore the computer to a point when the touchpad was working correctly.