You want it to use less RAM?
Here's how.
Start > right click "Computer" > Manage > Services and Applications >Services > Find "Superfetch" and right click, properties
Then, stop the process, and change Automatic to Disable.
Click Ok.
Restart your computer.
This will disable the program and file cache feature, freeing up RAM.
Also, just a note, that isn't idle. Paint, Firefox, Media Player, Messenger, Bittorrent and FRAPS don't count as idle.
Idle is a fresh boot with no background programs loaded.