yeah i do that all the time, cause i dont use my thumbs to type, never got on... well infact, i only use my index and middle finger on each hand to type, but i still type as fast as someone who is touch typing... go figure, its amazing what you can learn if you force your mind to do it.
anyway, i always find myself tapping what is an oversensetive trackpad with my thumb and moving the cursor, so i downloaded the proper synaptics driver and i reset for lower sensetivity.
you may try it. contact dell for the correct driver... or if you feel competent enough, go google it... synaptics... they make pretty much all touchpads... trademarked or something.