Originally Posted by trivium nate
its regular 64 bit vista and i tired taking a stick of ram out
I had this exact same thing happen to me when I first started using Vista x64. Grey's advice helped.
Have only 2GB installed, then do a fresh install of Vista x64. Download all your Windows Updates and drivers with only the 2GB installed. When it's all up to date, pop that last 2GB in and you should be good.
Also, double check that the memory re-mapping is enabled in the BIOS for the full 4GB