DO you currently have only 1 2GB module or are there 2 1 GB. modules ?? -- It might just be a case of having the 2 modules in the wrong 2 slots on the MOBO and so they are running in single channel mode - (from the CPU-z posted it would seem you have DDR3-800 modules and that seems strange as most DDR3 modules are at least 1066Mhz.)
Look at the SPD tab and see if it lists one 2gb. module or 2 1gb. modules and if it shows 2 modules try changing the slots that they are in so that both are in the same colored slots and it may change it to run in dual channel mode.
AS an Example -- in this Pic the Modules are set up in single channel mode since they are not in the same colored slots instead of running in dual channel mode by using the matching colored slots !!