memory - How do I determine which type of RAM my laptop uses?

I have a HP Compaq Presario CQ56-103ST laptop and I want to learn whether it uses DDR2 or DDR3 RAM.

• In its official web page, it is said that it has 3 GB DDR2 (1 x 1024 MB + 1 x 2048 MB).
  (Obviously not so. It has only 2GB of RAM installed in a single slot.)




• In this page, it is said that it uses DDR2 PC2-6400, DDR2 (non-ECC).




• Windows says that memory size is 2GB, doesn't tell about its type.
  (Yes, it is indeed 2GB.)




• CPU-Z says that it is 2GB DDR2 RAM.
  
  
  (CPU and Mainboard)




• Pictures I shot doesn't reveal any information to me.
  

It looks like to be DDR2, but I can't make sure about that. I don't have the user manual of the laptop with me right now. Can anyone please confirm it for me? I'm going to purchase new RAM units, I need to know the RAM type. If I order a wrong type of RAM, it will be a lot of trouble for me.

Answer

Check out wikipedia:
http://en.wikipedia.org/wiki/File:Laptop_SODIMM_DDR_Memory_Comparison_V2.svg

Then count the pins next to the notch to confirm that it is DDR2.
(Or check your picture. Enlarged it is easier to count and there are 20 pins before the notch).

Also useful to known: PC6400 aka DDR2-800 runs at 400 MHz (which explains your CPU-Z value)