Well, since you only got your computer for 400$. Witch you say it works fine for you. But if you gave some of us that computer, it would work horrible for us. Alot of people here use computers for Gaming/3D Rendering/Encoding ect. When you run those type of things, you need a fast computer. Rather your doing it for work, or personal use.
But for your computer to have less stress while runing them, you will need better hardware. Witch this cost more money.