Although I've never seen that much physical memory consumed by it....
There is often a BIOS setting that generally lets you dedicate an amount of memory to your graphics / video (GPU).
You might want to start by checking there.
There are a couple other things that come to mind....
One is a setting in msconfig where you can set max memory.
You might want to give RAMMap a try and see if that might help sort it out.
An advanced physical memory usage analysis utility that presents usage information in different ways on its several different tabs.
docs.microsoft.com