Computer Memory Upgrade

There are thousands of photos of my 3 daughters saved in the hard drive of my computer. They are photos of them from birth up until now. There are also videos of them that I had taken with my digital camera and downloaded into my computer. At the rate I am saving the photos and videos, I will run out of space in my computer in no time. The guy who usually comes to my house to fix my computer has asked me to upgrade my computer ram but I ain’t going to upgrade it just yet. Well, not until I have done some research on what RAM is and find out what upgrade is compatible for my computer system.