I have a computer running a BIOSTAR MCP6P M2+ 6.X motherboard using CORSAIR XMS2 4GB (2 x 2GB) Ram running windows 7 Home Premium 64 bit. When I first installed the Ram last year It showed up as 4 Gigs, however I recently noticed that it is only displaying 2.0 Gigs, in the My Computer Properties as well as CPU-Z, and in the POST. I have tested each stick individually in each slot and they work fine. However, when both are in only 2 gigs shows up. What might be the cause of this?