The maximum amount of Random Access Memory(RAM) that can be used in a computer totally depends on what computer you are talking about. Each computer has within it slots in which RAM sticks are placed into. If your computer has slots that are not being used up, you can place RAM sticks into those slots, but most computers come with the maximum amount of ram that can be used by it.
Although this is customize-able, and you could add more RAM slots to your motherboard, I don't recommend it, because first of all, what do you want more RAM for? All computers come with the necessary amount of RAM they need in order for them to function properly. And adding more RAM to your computer would mean that you plan on running programs/games which require more than just 'x' amount of RAM. So, before you do any of this, check with your manufacturer to see if adding more RAM to your computer is recommended. If not, just go out and buy yourself a better computer.
Now-a-days computers are being produced that come with up to 8GB of RAM. But these computers have specific uses. Everything integrated into them is needed.


