Here's a common question that we're having to answer with our customers over and over again. It's getting common because 4GB of RAM is no longer the big deal that it was a few years ago, and unfortunately with the extra memory comes extra overhead that may be preventing you from utilizing all that memory for your applications.
Need an explanation? Here's one of the most articulate articles that I've seen to-date on what's going on. Check out Mark Russinovich's recent blog post on Pushing the Limits of Windows: Physical Memory. Nice article, Mark.
Oh, and my 2 cent's worth (and my recommendation to customers)... time to start seriously considering 64-bit systems. ;-)
Agree with you. A good article and explain all.