As I said in the other thread you started where you asked the same question: You can but if you get a new CPU you'll have to get a new motherboard and if you get a new mother board you'll probably have to replace the RAM. At that point you've replaced half of the most important hardware. Dell is garbage anyway and there's no point in replacing parts to an old prebuilt computer. Trash the whole thing and build a new computer with an I5 2500, Z68 motherboard and at the very least 1333 mhz RAM. There's no point in dumping money into upgrading an old computer.