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Please list Dell model number and version of windows. Ex: Dell Inspiron 3543, windows 10

In the meantime, do you see Dell touchpad driver listed in device manager ?

Dell Inspiron 3543;

Hi thanks for replying,my Dell is Dell Inspiron 15 (3521) and my Windows is Windows 10,i cannot see any application about touchpad,only HID Mouse (my wireless mouse) appear there.

And also all synaptic driver is missing

Please expand Mice And Other Pointed Devices in device manager. At the taskbar, click on Action, and then Scan For Hardware Changes, hopefully touchpad driver appear. If that doesn't work, click View, and then Show Hidden Devices.

If the touchpad appears, tap it, click on Mouse, and then make the necessary adjustments, see image below:

If touchpad still doesn't show up, type Programs And Features onto [Cortana]search box, and then look for Dell Touchpad. Please let us know if you see it. If you see it, type Settings onto the search box, select Mouse & Touchpad, Additional Mouse Options, hopefully you'll see the image below:

Now, if Dell touchpad isn't listed in Programs & Features, I suggest you power off the system, remove all peripherals from system, remove wireless USB(mouse) receiver, AC adapter, and then battery. Press the 'Power On " button for 15 seconds to release Static Flea Power . Replace battery, adapter, and then power on system. Hopefully touchpad is working again. If yes, plug USB receiver back into system to see if touchpad still operate.  

Keyboard, touchpad, or mouse not working correctly | Dell US

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Lastly,

If all troubleshooting failed and Dell Touchpad driver still doesn't appears in device manager, I suggest you install Dell Touchpad driver from the link below. 

www.dell.com/.../DriversDetails

Device manager showing Dell Touchpad with mini exclamation mark(yellow) on the right,additional mouse option didnt show touchpad option.

cortana found no result on "Dell Touchpad"

Best regards,

azareein