All you can do yourself:
- Checking device manager for irregularites
- Reinstalling program/driver (you already did that)
- System restore back to when it stilll worked
- System recovery back to factory conditions.
If none of them help, it's a hardware issue and they (you?) need to replace the touchpad.
Synaptic Lux Pad V7.4 on PS/2 Port. Cursor works but tapping and L.H click does not work. Everything working ok with an external mouse on USB. Re-installed driver program for above but same problem. Please, need help