You might take a look at how much memory is allocated by Windows as 'Hardware Reserved'.
I have 32 GB of memory, but after noticing a lot of hard page faults, I went and looked and found that Windows went NUTS and set literally HALF of my total memory to be hardware reserved, so out of the 32 GB of installed RAM, I could only actually get at a little bit less than 16 GB.
(I did some searching, and found a Registry edit that resulted in my recovering nearly all of that reserved memory - IF you need/want more info on that please post back on that and I will dig up the thread I posted in the forums about it. I have to run out the door for the next 5-6 hours).
Bob Bone