I have a ASUS PTGD1-LA motherboard and when i switch on the PC, its only picking up 2040mb of the 2048mb memory. In windows it says 1.99GB installed and in dxdiag its 2040. I inserted one stick in to see what it was and the bios reports it as 504MB!

Program: eSupport.com BIOS Detect v1.2 July 21, 2003
BIOS Date: 08/16/04
BIOS Type: American Megatrends
BIOS ID: 63-0204-000000-00101111-081604-I915-A0125204
OEM Sign-On:
BIOS Date: 08/16/04 18:06:21 V
Superio: NSC 332 rev 8 found at port 2Eh
CPU Type: Unknown
CPU Speed: 3600 Mhz
CPU Max: 3600 Mhz
BIOS ROM In Socket: Yes
BIOS ROM Size: 512K
Memory Installed: 2048 MB (only 2040 is found)
Memory Maximum: 4096 MB