what is using the memory?

a week or so ago we bought 2GB new memory to max out 32 bit machine ( Foxconn Intel processor motherboard), but when we looked in Computer Properties, it said there was only about 2.27GB available for use - though 4GB is recognised. I thought Crucial must have sent us a duff stick. However, yesterday we maxed out another 32 bit machine, this one MSI Intel processor motherboard, and that too recognises 4GB but this time 3.25GB is usable. Both machines are running Nvidia graphics cards, which have their own RAM of course, and the Microstar doesn't even have embedded graphics - so where is quite a sizable chunk of memory going? Both are on Skt 775. Can you advise please?

thankyou HLPTech, we have downloaded that util on both machines, will come back when we have some results

yes, is/was our dog, we lost her to cancer some years back at only six and a half. Her name is Maisie.

We have both used Rammap, and had a quick look at the Sysinternals guide - but at the mo it doesn't mean a right lot to us - is there a particular area we need to focus our gaze please? PS the amount usable on the Foxconn is 2.75, not 2.27 as I first described..

which pages? will have to do it later as gotta go and feed everything that moves now. I will send some of the MSI readings. How do I put screenshots on here please?
Was reading another thread on here where the poster was having a similar problem, and he had to update the bios. Not sure we will be able to do that with these older machines - but one thing at a time :)