It obviously varies between model and brand but generally you can upgrade any memory and upgrade to a better battery pack. You can upgrade your drives to be CD burners, DVD burners, DVD players, etc. but only if all components match so heavily research your type or bring it into a computer shop for consultation before committing. Hard Disk Drives can be updated or fixed easily with laptops. Generally this is when there is a problem and you loose all of your data but at least its an easy fix. memory for one thing.