You can try it if you want. You may also have a bad memory controller slot on the board, so new memory won't work in one or more slots. I had that situation with 3 different rma boards once. Older memory actually costs more than ddr2 or ddr3; you have to decide if it's worth it. If you have the ability to change motherboards, you may be able to find a compatable board for your dell. Older chipset boards can be found that will work. You may be able to use an older Intel board if your case uses a standard form factor, such as micro-atx. List your dell model number if you want to pursue this course.
So basically it's the motherboard that's broken? The computer is 6 years old. I looked for a replacement for the motherboard and I couldn't find a new one. The used one I found was $300. lol Figures this would happen as soon as I lost my job. Doh!
Look for the same chipset of your dell system if you want to change out your motherboard. Computer geeks may have an Intel board with the same chipset. But for about $300-350, you can get a brand new computer. Walmart had an acer amd model with monitor for only $299 this morning.