"It basically never goes over 2GB of RAM used even though I have 4 gigs in the machine."
Actual used memory, my machine is sitting at 2.2GB at the moment. The rest is of course cached for other programs in anticipation of my opening of them, so I have a whole 28MB free. Those are of course pretty deceptive numbers in general. Having that extra 1.1GB over the 2.2 I am currently using means that I swap to disk a hell of a lot less than I would with only 2GB or even 2.5GB, or at least with 4GB it saves my disc swapping until
after the new program I want to open is already up and running. 3.3GB on a 32-bit system or 4GB on 64-bit is significantly more responsive than 2GB.
In short, a "used memory" readout of any sort tells you jack-all about how much memory is actually used in daily operation. Pull out 2GB on your machine and try to tell me that it doesn't suddenly feel rather sluggish.