On my system the more I add the more windows uses. Started with 64 and would have 4-8meg unused, went to 128 and would have 25-40meg unused, now I have 256 and there is 132meg unused. I doubt the swap file is ever used and that is a big plus. I think it uses what it needs and is less prone to give it back if there is unused ram.
Hardware911 - System resources are an entirely different thing than system memory. Adding more memory generally will not improve system resources. See this link about system resources: http://www.hardwarecentral.com/hardwarecentral/tutorials/83/1/
Adding more memory will improve your free system memory for running apps and so forth, but resources are more than memory.
Maybe I misunderstood, but I hope this helps!