I'd say none of that is going to play BF3 well at the moment. The biggest improvement you are going to get though is to get 4GB RAM, HD 6850/HD 6770 depending how many PCI-e connectors your PSU has then overclock your CPU.
Toms did an article showing the game is very gpu limited and even a relatively modern dual core cpu can run it. So I would try to just upgrade the video card for now if you need more performance look towards a new cpu/mobo/ram.
For bf3 I would look at no less than a 6870 to run the game well.
My god you wanna BF3 on this crap eith a ddr2 ram.don't even fream abou ityour system is very old you van play vice city on it.
you need complete updation.
try this config
1.intel i3-3220/amd fx 6300
3.mobo with usb 3,sata,hdmi
5.to add all these you will need a decent PSU 0f about 400-5500w