Unfortunately, even if you disable the "Touchpad (I believe it is call Synaptecs)", the problem will still exist. It may not be that you ever used your touchpad, but by resting your palms on it to type, etc causes pressure on it.. I guess to prove the point of whether this is the problem is, disable it in the BIOS, (Search Dell's WEBSITE under support, I know you will find many of complaints about it on their forums) and then plug in your optical mouse.. if the problem is gone than that's it, if not let me know..