NO NO NO.. You need not disable your mouse pad NOR drag around an external mouse.
ALL YOU NEED is a very very cool program called "TOUCHFREEZE"
It is very small, consumes very little resources running in the background;
it detects any time you are typing, and ONLY then, it DISABLES your mousepad TEMPORARILY and within a split second it enables it again as long as you are not hitting keys on your keyboard!
I don't work for them or anything like that. I have just tried all the solutions and dragging around an external usb mouse and everything else I could imagine trying, and I LOVE THIS PROGRAM, it is THE solution to this problem you have and I USED to have!
Hope I have helped you.
Go to Google and enter "Download TouchFreeze"... it should be the first result