The total amount of memory, or RAM, that a computer can have is dependent on the motherboard installed in the computer and the operating system. In general, most motherboards will support either two or four sticks of RAM, but the type of memory can differ widely from one motherboard to the next.
First, identify your motherboard, specifically the brand and model number of the motherboard. Open the computer case and look at the motherboard to find the brand and model number. It is often printed on the motherboard in white or yellow letters, so that it is more easily found and readable.
Next, search the Internet for that brand and model number, to find specifications of the motherboard, including the type of memory and the total amount of memory supported.
Once you know the type of memory and total amount of memory the motherboard supports, you can choose to increase the amount of memory by installing additional sticks of RAM or replacing existing sticks of RAM with ones having a higher amount of memory.