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Enable the touchpad
If your laptop's touchpad isn't working when you try to use it, you may have accidently pressed the keyboard shortcut combination (Fn + a key), or the dedicated key which disables the touchpad. Also, if you have recently upgraded your laptop to Windows 10, it is possible that your touchpad is disabled. All you need to do in both cases is to enable it.
You can enable the touchpad using keyboard shortcuts (key combinations on the keyboard, e.g. Fn + a key), or via the operating system itself (Windows, MacOS).
Start -> Control Panel -> Mouse -> Click on the touchpad tab (Synaptic, Elan and etc.) -> Enable the touchpad
Start -> Settings -> Devices -> Mouse & Touchpad -> Scroll down to Related Settings and click Additional mouse options -> When the mouse properties window pops up, click on the ELAN (or SYNAPTIC) tab -> select your device and click Enable
Click the Apple logo at the top of the screen -> System Preferences -> Universal Access -> Select the Mouse & Trackpad tab -> Trackpad Options -> clear the Ignore Built-in Trackpad checkbox
The outdated chipset drivers may prevent your touchpad from working properly. They are the "bridge" between the CPU (the processor) and all the other components that comprise your computer. That is why it is very important to keep them updated. Updating the chipset drivers is a good solution to this problem.
Maybe a program you recently installed prevents your touchpad driver from functioning properly or is responsible for the touchpad scroll not working issue. Cleaning the registry should help you solve the problem.
If your touchpad started misbehaving after you have installed or updated the touchpad driver, it is possible that something went wrong with the driver-installation process. To fix this issue you need to reinstall the driver.
Note: The best way to uninstall software (in this case, driver) is via uninstaller software. The uninstaller software uninstalls the driver (or software) and performs a thorough scan for leftovers. Sometimes, among those leftovers there are settings that will remain when you install the "fresh" driver and that might cause a conflict again.
Maybe an external USB device (e.g an USB mouse) automatically disabled the touchpad. Turn off the laptop, disconnect all external devices and then, turn it on again.
If the touchpad starts working, that means that one of the external devices prevented it from working properly; however, if your touchpad still doesn't work, then something else is the problem (check out the other solutions).
If you have bought a new laptop and you experience problems with the touchpad, take it back to the store and have it re-examined by the technical staff. They will diagnose the problem, repair the touchpad, or provide you with a replacement (if they fail to repair ir).
Run the Hardware and Devices troubleshooter (Windows)
Windows has a troubleshooter which can locate and fix the problem with your touchpad, instead of you. All you need to do is to run it.
To run the Hardware and Devices troubleshooter do the following, go to Start -> Control Panel (or type control panel in the start menu search box) -> type troubleshooting in the search box -> click on Troubleshooting -> Hardware and sound -> run the troubleshooters one by one.
Note: Do not interrupt the troubleshooting process.