Jumping cursor is driving me MAD!

I had to reformat my Toshiba laptop a while ago as it was going slow. It works fine now, except that the cursor jumps about randomly as I'm typing. I did a bit of googling to try to find a solution but the only couple of solutions I found made no difference. I've tried slowing the speed, make sure I'm not accidentally resting on the mouse pad.... Still it jumps. (just now, it jumped from the middle of "difference" to "now" in the first line. Any help gratefully appreciated. Maybe it can't cope with a fast typist?