I had the same problem after purchasing an HP laptop with a Synaptics TouchPad. After using a wireless mouse for awhile, the TouchPad stopped working. The TouchPad light was white, indicating it was enabled. No TouchPad devices was listed anymore in the Mouse Properties in the Control Panel. I tried reloading the driver but nothing changed.

After shutting down the laptop and removing the battery (according to owner’s manual) it worked again. After turning on the laptop, make sure the TouchPad works. Then go to Control Panel, Mouse, Device Settings tab, and make sure a Synaptics TouchPad is listed in the Devices list and that the Enable button is grayed out.

Go to 'Control Panel' and double click on the mouse icon. A window should open with several tas across the top. The last one on mine is "Touch Pad On/Off". Select that one if you have it. There you should e able to turn the settings back on. If you don't have some of this I think you need to reinstall your touch pad driver. If your computer is quite new, I suggest you go to the Dell web site and download the latest driver for your touchpad if you can. Some sites don't have drive downloads any more or your computer is too new that they have not set up driver downloads for it. Best of luck.