I am having the same issue as of recently. More than 50% of my RAM is used even when nothing else is running, and when I start using any additional programs, even if it's just a browser, it goes to almost 100%, slowing my computer down so much, that it is making my job very difficult.
I also cleaned and removed all unnecessary programs and processes that may be causing it, but the issue is not solved. I have Windows 7 Ultimate, 32bit.
What you saying that Windows 7 memory manager is taking up that much memory, but that it should free it up for anything else that needs it. But the memory doesn't free up for me, any additional task takes up additional memory.
Do you have any idea what may be causing this?