Windows 7 is using 2MB "Large Pages" and these are not broken down to 4k pages until the memory pressure is around 90%.
You can disable large pages and see the difference, you will have slightly reduced performance though.
In the advanced setting you can modify Mem.AllocGuestLargePage (1 to enable and support both large and small pages – the default, 0 to disable and force small pages)
// Linjo