I have been struggling to disable the tap to click function for the touchpad under Windows 8 on my Aspire 5920 laptop. The native windows driver does not have this option and Acer do not want to support windows 8 for the Aspire (Even though it passed the windows compatibility test before I installed Windows 8).
Thankfully the touchpad software developer Synaptics still supports its customers after more than a couple of years and you can go to their website and download the latest Windows 8 driver. Its has plenty of different options including the option to turn off tap to click.
So if you want the latest driver for your touchpad - its at version 18.104.22.168 and the driver covers Vista, XP, 7, 8 32bit and 64 bit versions. I can confirm that it works fine with the Aspire 5920 but as its not built specifically for any one make/model you might want to set a restore point before installing. You must uninstall any previous Synaptics touch pad drivers before the new install.
The latest driver from Synaptics (v17_0_19_C.....) will not install on my Aspire 4370Z running windows 8.1. I have not found a driver that will allow me to do anything but define the left and right buttons. I've lost the ability to scroll with the touchpad and cannot turn off tapping.