First, try turning off the laptop, and connect an external (USB) mouse. Then follow the instructions below, and once done, shut down the computer, disconnect the external mouse and restart the computer.
Try the following and see if it fixes it...
1. Go into "Control Panel".
2. Click "Hardware and Sound".
3. Now click "Mouse and Touchpad".
4. Now go to "Additional mouse options".
5. The Mouse Properties window will open. In here click on your device.
6. Make sure your device is set to enabled. If it isn't then click "Enable Device".
7. Exit both that screen and "Control Panel".
Also, you might want to check for updates to your drivers, including the Synaptics drivers.
If this does not help, and an external mouse works fine, then it...