Touchpad not responding to tap

Inspiron 4100 xp home

My touchpad stopped working yesterday evening. I can see and move the cursor but when I tap on the pad there is no reaction. I cannot use it to send a command. I have synaptics touchpad installed and the latest update. I have found a mouse and that works fine. I booted to the diagnostics cd and ran a test on the one device. I got a couple of boxes. I moved the cursor to the left box. It was clear and then filled with colour. I clicked on the arrow on the keyboard and tried the right box. It didn't fill with colour. In fact nothing seemed to happen. I was left looking at the same screen. In the end I aborted the test. I have the feeling that it's a hardware problem with the touchpad.

Would anyone have any help, comments, suggestions please?