Yes, Bios can detect my Ram at DDR2 400 (800 Mhz ddr). But due to CPU limitation, which has a 10.5 clock mutiplier and a memory divider of 6, the maximum frequency my CPU can handle is 351.6Hz (703.2 Mhz ddr) at normal stock setting.
What I mean is that my Bios can detect my RAM's maximun frequency but can only allow a lower frequency due to my CPU limitation. I can't overclock my CPU since it is not supported by my motherboard.
Thus this frequency limitation the cause of the problem or can there be any other cause?
I have Win XP Pro 32 bit and my system only reads 3.25Gb of ram. The reason for this is due to the OS not being able to allocate all 4GB. In order for your system to read 4GB or more you need a 64 bit OS.