The motherboard specifications indicate 400 DDR... but my motherboard seems to be 3.3V indicating it's made for SD RAM, and it seems to currently have SD RAM installed. I am pretty sure that this board can have both SD RAM and DDR installed, bt not both at the same time.
Thanks caperjack. I was getting quite confused. The manual and the motherboard specs were leading me to believe that it was SD RAM compatible too. There was also the fact that the motherboard memory module was 3.3v (the specific voltage of SD RAM).
I hope the DDR 400 I buy is compatible, otherwise I will have bought an expensive, and fairly useless pair of paper weights.