Hard to say. I recommend that you should go out and buy a new MOBO and i3. The thing is that if your motherboard is outdated and old, don't get the old stuff to fix it because you will pay more to fix it then it would cost to get a newer and faster system.MotherboardProcessor
I would agree with that, UNLESS you already have the CPU. If you don't have the CPU than I would upgrade to an socket 1155 Pentium/i3/i5/i7 and new z77 based mobo, if you have the $ to do so.
I currently have a e6700 CPU in a s775 system and I also have a Q8300 CPU waiting to go into it, so I'm potentially in the same boat as you. I fortunately don't have a Dell mobo (which can be restricting on what you can do) so I won't possibly have as many restrictions that you might have (as far as upgrades go).