Well I had this problem of my cursor jumping randomly while I typed, and hadn´t found a good solution, but this guy really found the answer, so if you want you can go to the link and follow the instructions (nevermind the "Content Warning" apparently software and computers are not his major interests, but anyway he found the solution to this problem that seems to affect a lot of people with laptops):
Or read the short version:
The problem is that Windows 7 by default uses the PS2 Mouse driver for the touchpad instead of using the proprietary driver. So you should:
1-Find the appropriate driver for your touchpad and download it. (It should be in the manufacturer's website)
2-Uninstall the PS2 mouse driver, BUT DON'T REBOOT!
3-Install the proprietary driver. And reboot.
After this, you should have the touchpad's software, and the problem should be gone. (Anyway, if you have an external mouse, you can use that software to disable the touchpad)