Is pentium d 820 works on ddr2 motherboard

You need to supply the make and model number of your motherboard. The chipset used would be helpful.

The Pentium D 820 is a dual core LGA775 CPU.
It is will work with any LGA775 motherboard that has an Intel 945 or newer chipset.
Virtually all of these motherboards run DDR2, only a few of the latest supporting DDR3.

Did you have a specific motherboard in mind or is this just a general question?

intel pentium D 820 is the first generation dual core processors, it is not just good as the core 2s