Frustration with touchpad for Inspiron 1521

My left mouse button doesn't seem to work on my mouse pad.  It clicks when I press it, but nothing happens.  I reinstalled the driver that came with the computer, that didn't help.  I plugged in an external mouse, which works, and I reset the controls to use the right button as the click button.  Any suggestions on how to fix the touchpad?  Thanks in advance for your help