I am from Dell Social Media and Community,
You can enable the touch pad in the driver settings — Using the external mouse (or key strokes if no mouse is available), go into the Dell Touch-pad Properties. Go to the Device Select section and enable the touch pad. If already enabled, get the latest driver from support.dell.com and install it. This should get you going.
If not, test the device in Dell 32-bit Diagnostics — To eliminate a potential software problem, run the Dell 32-bit Diagnostics from the F8 menu and test the device here.
Let me know if this has fixed your issue or if you need any further support.