I thought I understood why more than 3gb of RAM has little value in modern machines, but it turns out I was wrong. Dan explains nicely:
Large areas of the memory between three and four gigabytes are cordoned off for system devices in exactly the same way that chunks of the Upper Memory Area were purloined in the old days.
*shudder*. I remember struggling with memory areas as a kid, and never really understood what was happening. It wasn’t until my A+ exam a few years ago that I finally got to grips with it. I think I’ll recommend memory-hungry clients top out at 3gb for the meantime – there doesn’t seem to be an easy way around it without going 64-bit, which brings many other difficulties.