Many laptops and netbooks do not come with a disable touchpad button. There is no other easy way to disable the touchpad while you are typing or using an external mouse. This can cause wayward mouse movements while typing as the touchpad is pretty sensitive and sudden mouse movements can cause wayward typing.
Enter Touch Freeze, a useful and freeware utility which will automatically disable the mouse touchpad while you are typing on the keyboard. The touchpad will automatically be reactivated when you stop typing.