First and foremost, let me dispel the notion that “more files” means a slower computer. It doesn’t matter if you have 5 pictures, or 100 pictures, or 10,000 pictures… at least for the most part. The same is true for music, documents or anything else.
Why doesn’t this matter?
There are TWO places in your computer that can be referred to as “memory”; the Hard Drive and your RAM. These serve completely different purposes.