The problem is that for no reason windows is using a lot of RAM for no reason. I tried to determine the source with taskmanager and resource manager, accumulated I counted 900 mb of RAM (all users checked offcourse). When I start to instal more stuff my RAM skyrockets to 2 - 3 gig of memory.. My CPU stays low and shows no sign of usage.
So Windows is using ram the way it should I do not see what you are having a problem with. Windows 7 will free some of that memory when needed unless your system is slowing down or consuming all of your ram for no reason then I would not worry about 2-3gig as it is perfectly normal.