I have this program called "RAM Page" on my computer. It runs in the System Tray - Lower right corner of the screen - and it displays how much free RAM I have at any given time. I can view details and it tells me total RAM, Free RAM, Total Page, Free Page, Total Virtual, and Free Virtual. I don't know what that means or how this thing works, but whenever things are running slow (the free RAM is below 200) I just double click it and a few seconds later my free RAM is back up to like 400.
You might consider getting it, I will see if I can find the site.
EDIT: Right after I said "I will see if I can find the site" I found the site even though I had been searching for 5 minutes prior.
Anyway, here is the site if you want it.
http://www.jfitz.com/software/RAMpage/index.htm