There isn't anything to make your computer use more RAM... It just depends on the programs using it... Try opening a couple of tabs in IE7 or Firefox, media player and a couple of apps and you should see it go up.
I've got IE7 (3 tabs) media player and Fireworks open and I have 600MB left... I don't think it's a problem
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Intel Core 2 Quad Q6600 @ 3.4Ghz
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