There are a few boards that will see two sets of dimm slots with one pair being for 184pin DDR memory and the other for the 240pin DDR2. That just explained where you can see DDR memory used only on some boards only. But on those you have to choose between one or the other. For a DDR2 240pin only board the answer is obvious. You can't run DDR 194pin memory on it.
One free system information tool that will tell you the exact model board as well as what cpu you are running and even temps is SIW found free at http://www.gtopala.com/ Once you know the exact model you can look over the specifications to see what it does support for memory. An Intel model using that same chipset lists the following.
Different number of pins, different keys. As PC Eye said, there are some boards that support it, but I'm quite sure none use the Intel chipset. I beleive those that support both are VIA based.
One of the few boards seen that have slots for both types are made by Asrock and essentially lower quality boards there. Those simply allow you to use older memory when you build a new case to save on cost. But then you end up replacing the memory when wanting performance. The SIW tool at the link will tell you literally everything about the system including what programs you have installed. Once the window is open you simply click on motherboard to see the complete information come up.
In ready agreement there! Every board looked at says DDR2. The SIW tool will specify make and model where you strictly go by the specifications for it. Meanwhile I'm trying to decide on a DDR2 800 supported board for running the AM2 6000+ X2 model. The models seen for the 945P chipset point at 667.