Help..GiGA Byte GA965DS3 sys info shows 2GB RAM as 1GB RAM

Hi,
Im a newbee and i just assembled my system based on Gigabyte GA 965 DS3. I used 2 X 1 Gb Kingston DDRII ram at 667 Mhz (KVR667D2N5/1G) in slots 1 and 3. System is stable and works fine. The BIOS screen detects the RAM as 2048 Mb and a quick properties check in windows (my computer) reaveals the Memory at 2 Gb and the Windows Task pane gives the same information. But the problem is that when i check the windows system information utility, it gives the following:
Total Physical Memory: 1024.00 Mb
Available physical memory: 1.35 GB
Also the 3D mark 06 gives the following info about memory:
Memory Info
Total Physical Memory 1.98 GB
Free Physical Memory 1.34 GB
Memory Slot 1/4
Installed Enabled Size 512 MB
Form Factor DIMM
Frequency 667.0 MHz
Slot A0 [Bank0/1]
Type Details -
Enabled Size 512 MB
Total Bit Width 64 b
Data Bit Width 64 b


Memory Slot 3/4
Installed Enabled Size 512 MB
Form Factor DIMM
Frequency 667.0 MHz
Slot A2 [Bank4/5]
Type Details -
Enabled Size 512 MB
Total Bit Width 64 b
Data Bit Width 64 b


Im really confused and would appreciate if someone could help me out in this regard. Does it mean that my system is treating the 2 Gb memory as 1 Gb? I hope its not like that or maybe im missing on something.

Thanks in advance.