I recently bought 2x1Gb memories which I tried to install on my mobo. Unfortunately they didn't work quite as well as expected, so I simply decided to keep my 2x512mb (plus the 2x1Gb I've always had).
Ever since though, my motherboard is acting weirdly. Somtimes, after complet shut downs, every time I try to run the computer, my mobo fans and lights turn on, everything turns off for a split second, then powers up as normal. After this weird event, I'm always unable to start Vista as I keep getting a blank page after the green loading bar.
This wont happen when I boot into Safe Mode, because when I restart the computer while in Safe Mode, the mobo acts naturally, making it possible for me to boot into Vista.