At this date, any RAM over 8GB even with a Windows 7 x64 OS is wasted unless you have an application (not a game) that is specifically programmed to use that much RAM. Otherwise, most games, even the newest beasts such as Skyrim, will only use 4 GB and then switch over to the Page File.
Are you running multiple VM's or something Japo!?
In a server instance running VM's is the only time I'd see the need for that much RAM.