I think I have found my answer from this link http://forum.corsair.com/v3/showthread.php?t=67972
I need to enabled the "Memory Remap" feature in BIOS before installing Windows 7 64 bit. If I want to boot into Windows Vista 32-bit, I have to disabled it. I think I'll just have Windows 7 64 bit on a 80 GB SSD. I won't dual boot. I was thinking of upgrading to 8 GB but the price of DDR2 800 is equal to much faster RAM, so I'll wait until I have a new motherboard and cpu.