Why is my Asus P5PL2-E using 640MB of RAM (out of 4GB)? [duplicate]

Why is my Asus P5PL2-E using 640MB of RAM (out of 4GB)? [duplicate]

I've recently installed 4GB of RAM on my server, which is running Windows XP SP2 32-bit and My Computer showed that only 3.37GB were installed. After digging Google for a bit, I couldn't find anything helpful, but I do remember reading a post in a forum regarding the motherboard using 640MB of RAM. Digging in my own BIOS, I've also found that my motherboard has also reserved that amount for its self.