GA-K8NS Ultra-939 -Dual ram Problem

I got GA-K8NS Ultra-939 , I have 2 kingston 512MB DDR400 3200 CL3 ,
one ram is Double Side , second is Signle Side.
The problem is when I got the ram in the slots (Slot 1 and Slot2 which I checked in the motherboard book in what slots I can put DUAL and how + it shows that it doesn't matter if its DD/SS) I dont see in Windows XP and when the computer start that I have 1028MB, it shows 512MB.

When computer run at start it shows that everything is fine expect 1028 MB:
Memory Testing : 524228K OK
Memory Information: Dual Channel , 128 BIT (when not dual 64bit)
DDR Dual Channel Enable

*In a program "CPU-Z" it shows I have 1028 MB dual
*I tired changed to slots 3&4 and its the same
*I upated last bios update

thanks a lot