I can't seem to disable tap to click on my dell studio 1555 laptop (windows 7- 64bit). Every time I disable it, it will come back on a minute later. This has never been a problem until two days ago. I have uninstalled the synaptic driver and reinstalled the latest version, but the problem still persists. I also am running "twofingerscroll", though I have had that for years and this problem didn't start until 2 days ago.
Since this is a recent problem I suggest running system restore. Click the start button, click search, type in system restore and press enter. Once you have system restore open look for a restore point that was created before you noticed the poblem. See if it helps, for more on system restore please check the following link.