Recently I upgraded my currently installed Synaptics touchpad driver to version 15.x, and I found that I cannot emulate the middle-click effect by pressing both right and left click buttons. I found no options in the settings to enable that functionality. Finally after searching the web I found a workaround here [+]:

  1. Run the registry editor (regedit)
  2. Go to key: HKEY_LOCAL_MACHINE\Software\Synaptics\SynTP\Defaults\
  3. Here create a new key as a DWORD and name it HasBothButtonFeature and set the value to 1.
  4. Log off and Log on again

It worked fine for me.