I have Windows XP Pro installed with all the updates. I have an Asus P5ND2-SLI Delux motherboard (it takes DDR2 533 and 667 memory). I had 2GB of DDR2 533 memory; I removed those and installed 4GB of DDR2 667 RAM (Kingston KHX5400D2K2/2G). When Windows XP runs, it shows 2.25GB of RAM only!! The BIOS sees 4GB of RAM and I ran Asus PC Probe and it sees all four 1GB modules (a total of 4GB) ... what shall I do to get XP to see the 4GB of RAM? Shall I reinstall? Please, help!