From a computer website:
The whole cursor jumping issue with laptops isn’t that uncommon and it happens to pretty much anyone who uses their laptops frequently and use the onboard keyboard. The problem occurs when you get too close, or even touch, the touchpad when you are typing. Many touchpads can register heat meaning you don’t even have to touch the touchpad in order for the cursor to jump around the page. The problem is more common with newer computers when the touchpads seem to be the touchiest. After a while the sensors in them seem to fade away a little bit and the problem seems to go away on its own.
There are a few things that can be done to fix the cursor jumping problem on laptops.
Fix 1: Don’t use the internal keyboard. Use an external keyboard for typing. This doesn’t work in every situation as maybe you want to sit on your couch in front of the tv while surfing the internet. A keyboard would just get in the way. But if you’re at a desk, consider using an external keyboard.
Fix 2: Change the sensitivity settings on the touchpad. On most laptops you can do this by clicking the Start Button and clicking Control Panel. Switch to the Classic view if you’re not already in it (Windows XP). Double-click Mouse. From here it’ll usually open up to the touchpad settings but you may have to navigate further if that’s not the case in your environment. Look around where it mentions sensitivity and change it so it requires a heavier touch to register the touchpad. In most cases this alone will fix the problem.
Fix 3: In my experience I’ve known a lot of professionals who work in the field. One of their favorite fixes is placing their business card (or a couple of sticky notes) over the touchpad while they’re typing. When they need to use the touchpad, they simply remove the business card and type away.