The answer to this question depends on three things. One is whether or not the computer in question is open for modification, two, how high the default RAM in that computer actually is, and three, what hardware upgrades are available. Before reading any further it should be noted that this information was written assuming the reader has a basic knowledge of computers and their components.
If your computer offers you access to do so, opening it up will probably provide you with all the room necessary not only for upgrading RAM but also other internal components such as hard drives and graphics cards at some point when needed. If necessary, however, removing items like your DVD drive will offer additional room within your machine which can be used either to upgrade RAM.