Mathjac, Drane is right in suggesting a new computer.
If your budget is limited, beefing up the old one might be a start for a new build. However, instead of being restricted by a low profile card and an inadequate power supply, get a standard tower case. Even good quality new ones can be quite inexpensive. Your Dell motherboard should fit in with ease as well as your hard disk and RAM sticks. The optical drive seems to be of the laptop type, but they cost only $15 or so. Then you'd only need a decent video card and an proper power supply.
Later you can get a new motherboard, CPU and RAM when needed.