My machine has plenty of power and I literally am running a fresh install of Windows 7 x64, but notice that I idle around 28% on my 4GB of RAM at all times.
Thats not a problem unless you are experiencing a slow computer. What your seeing is Superfetch in action. Superfetch is designed to keep some of your most often used apps in memory when it thinks your going to need them based on previous uses.
If you ever ran into a low memory situation windows would very rapidly clear out that Superfetch gathered data to provide room for RAM hungry applications.However if it's really bothering you you can turn Superfetch off but I wouldn't recommend it unless you play hardcore 3D games you won't need that memory that suddenly, and you will...
