Hi everybody!
I think I have the same problem with RAM memory 
. The desktop board is D945PSN.
I have installed three 1GB-module (total 3GB), but in the BIOS screen I get the following:
Total Memory: 2048MB
Memory Mode: Single Channel
Memory Channel A:
Slot 0: 1024MB (DDR2 667) SPD: 5.0-5-5-15
Slot 1: 1024MB (DDR2 667) SPD: 5.0-5-5-15
Memory Channel B:
Slot 0: 1024MB (DDR2 667) SPD: 5.0-5-5-15
Slot 1: Not Installed
But when I start Windows (XP), and go to System Properties, it shows me 3GB of system memory! 
Thank you.