The memory article at http://www.aumha.org/articles.htm might help, but in VM based OSes, the idea is to have no free memory since such would be wasted memory. If one was to be able to keep 256M free out of 512M on a certain OS, what difference could there be if you had 0 bytes free on 256M? To limit the application/OS to keep free memory on a VM OS is well discussed and the idea of free memory is a DOS legacy item.
In short, RAM beats hard disk speed everytime. As such, try to use all the memory.
I am running a four-year old PC with a new pentium 4 2.0 Ghz processor, 256 MB of DDR266 RAM and an nVidia TNT2 with 32MB RAM.
I run Windows XP with service pack 1A. I also use cacheman, a utility that shows you how much RAM is used and free.
Cacheman shows me that over 55% of my total 256 MB RAM is being used when I have absolutely NO programs running.
Is something wrong with my machine or the memory sticks or is the application just inaccurate?
I cannot currently afford to upgrade my RAM.