whats the differents with ddr and sd?
 

actually why are ddr and sd so different? one is better and cheaper and one more is more expensive and hard to find?

SD ram is harder to find because they don't make it anymore. It's an older and slower style of ram. DDR ram supports higher communication speeds and is now the industry standard.

oh... that means if i wanna get a windows XP or something i need to get a ddr then sd?